Document And Entity Information
Derivatives Not Designated as Hedging Instruments [Table Text Block]
Note To Financial Statement Details Textual
Significant Accounting Policies
Note 1 - Basis of Presentation and Accounting Policies
Hedging Relationship [Domain]
Note 5 - Income Taxes
Note 6 - Derivative Instruments and Hedging Strategies
us-gaap_SecuredLongTermDebt
Secured Long-term Debt, Noncurrent
Cash Flow Hedging [Member]
Note 7 - Fair Value Measurements
Note 8 - Warrants
Note 10 - Noncontrolling Interests in Subsidiaries
Not Designated as Hedging Instrument [Member]
Note 13 - Share Based Compensation
Note 15 - Segment Information
Income Tax Disclosure [Text Block]
Hedging Relationship [Axis]
Note 1 - Basis of Presentation and Accounting Policies - Deferred Revenues (Details)
Note 1 - Basis of Presentation and Accounting Policies - Property and Equipment Useful Life (Details)
Hedging Designation [Axis]
Note 1 - Basis of Presentation and Accounting Policies - Deferred Gain Activity (Details)
Hedging Designation [Domain]
Note 1 - Basis of Presentation and Accounting Policies - Accumulated Other Comprehensive Income (Details)
Designated as Hedging Instrument [Member]
Note 5 - Income Taxes - Income Tax Rate Reconciliation (Details)
us-gaap_LiabilitiesCurrent
Total current liabilities
Note 6 - Derivative Instruments and Hedging Strategies - Derivative Instruments (Details)
Note 6 - Derivative Instruments and Hedging Strategies - Gains (Losses) on Derivative Instruments (Details)
us-gaap_GuaranteeObligationsMaximumExposure
Guarantor Obligations, Maximum Exposure, Undiscounted
Note 7 - Fair Value Measurements - Assets and Liabilities on Recurring Basis (Details)
Other current liabilities
Note 7 - Fair Value Measurements - Estimated Fair Value (Details)
Payments received on third party notes receivable, net
Note 7 - Fair Value Measurements - Other Assets and Liabilities at Fair Value (Details)
Note 8 - Warrants - Warrant Activity (Details)
Note 10 - Noncontrolling Interests in Subsidiaries - Noncontrolling Interest (Details)
Note 13 - Share Based Compensation - Equity Incentive Plan Transactions (Details)
Note 15 - Segment Information - Summary of Reportable Segments (Details)
Note 15 - Segment Information - Income (Loss) in Equity Method Investments (Details)
Notes To Financial Statements
Notes To Financial Statements [Abstract]
Share-based Compensation, Activity [Table Text Block]
us-gaap_DerivativeNumberOfInstrumentsHeld
Derivative, Number of Instruments Held, Total
Granted (in shares)
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Guarantor Obligations, Nature [Axis]
Guarantor Obligations, Nature [Domain]
Current portion of long-term debt
Proceeds from issuance of long-term debt, net of issue costs
us-gaap_OtherComprehensiveIncomeLossTax
Income tax benefit
Income tax expense
Other comprehensive loss
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]
us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
Total equity
Balance
Balance
Accounts payable and accrued expenses
Deferred revenues
Accrued wages and benefits
Accrued income taxes
Director share awards
The amount of expense for director stock awards.
smhi_StockRepurchasedDuringPeriodValueExerciseOfWarrants
Exercise of Warrants
Equity impact of the value of stock that has been repurchased during the period, due to the exercise of warrants, and has not been retired and is held in treasury.
Supply Vessel Previously Retired [Member]
Related to supply vessels previously retired and removed from service.
Revolving Credit Facility [Member]
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Outstanding as of December 31, 2017 (in shares)
Outstanding as of September 30, 2018 (in shares)
Proceeds from exercise of stock options and Warrants
Amount of cash inflow from exercise of stock options and warrants granted.
smhi_RestrictedStockVesting
Restricted stock vesting
The value of restricted stock that has vested during the period
smhi_ClassOfWarrantOrRightExercisedDuringPeriod
Class of Warrant or Right, Exercised During Period
Warrants exercised, weighted average exercise price (in shares)
The number of warrants or rights exercised during period.
smhi_SharesPaidForTaxWithholdingForExerciseOfWarrants
Shares Paid for Tax Withholding for Exercise of Warrants
For net-share settlement due to the exercise of warrants.
Credit Facility [Axis]
Warrants and Rights [Text Block]
The entire disclosure for warrants and rights.
Proceeds from disposition of property and equipment
Proceeds from Sale of Property, Plant, and Equipment, Total
Credit Facility [Domain]
Warrants issued, weighted average exercise price (in shares)
The number of warrants or rights issued during period.
PIPE Warrants [Member]
Related to the PIPE Warrants.
Warrants exercised (in dollars per share)
Class of Warrant or Right, Exercised During Period, Exercise Price
Exercise price per share of warrants or rights exercised during period.
us-gaap_PolicyTextBlockAbstract
Accounting Policies
Carlyle Warrants [Member]
Related to the Carlyle Warrants.
Merchant Navy Ratings Pension Fund [Member]
Related to the Merchant Navy Ratings Pension Fund.
smhi_MultiemployerPlansCumulativeFundingDeficit
Multiemployer Plans, Cumulative Funding Deficit
Amount of cumulative funding deficit attributable to the pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.
Warrants issued (in dollars per share)
Exercise price per share of warrants or rights issued during period.
Shares Available for future grants as of September 30, 2018 (in shares)
us-gaap_PaymentsToAcquirePropertyPlantAndEquipment
Payments to Acquire Property, Plant, and Equipment, Total
Purchases of property and equipment
us-gaap_IncrementalCommonSharesAttributableToConversionOfDebtSecurities
Incremental Common Shares Attributable to Conversion of Debt Securities, Total
Current Liabilities:
Treasury Stock [Text Block]
us-gaap_Assets
Long-term debt, including current portion
Property and Equipment:
Fleet Utilization
The percent of utilization of the company's fleet during the period.
Average Rates Per Day
The average charter rates, per day, for vessels chartered by the company.
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]
Fleet Available Days
The number of days the company's fleet was available during the period.
Equity Award [Domain]
Performance Guarantee [Member]
Restricted cash
Award Type [Axis]
us-gaap_NetIncomeLoss
Net Loss attributable to SEACOR Marine Holdings Inc.
Restricted Stock [Member]
Net Income (Loss) attributable to Noncontrolling Interests in Subsidiaries
Net Income (Loss) Attributable to Noncontrolling Interest, Total
us-gaap_InterestCostsIncurredCapitalized
Capitalized Interest Costs, Including Allowance for Funds Used During Construction, Total
Employee Stock Option [Member]
Director Stock Awards [Member]
Related to director stock awards.
Antidilutive Securities [Axis]
Antidilutive Securities, Name [Domain]
Receivables:
Comprehensive Income (Loss) attributable to Noncontrolling Interests in Subsidiaries
Commitments and Contingencies Disclosure [Text Block]
us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
Accumulated depreciation
us-gaap_PropertyPlantAndEquipmentNet
Net property and equipment
Historical cost
Construction in progress
Long-term Debt, Type [Axis]
Long-term Debt, Type [Domain]
us-gaap_EquityMethodInvestmentOwnershipPercentage
Equity Method Investment, Ownership Percentage
Derivative assets
Derivative Asset, Total
Net loss
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total
Net Loss
us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest
Comprehensive Loss
Embedded Derivative Financial Instruments [Member]
Derivative Instrument [Axis]
Derivative Contract [Domain]
Cash Flows from Investing Activities:
smhi_ProceedsFromSaleOfPropertyPlantAndEquipmentExcludingDepositsForFutureVesselSales
Proceeds from Sale of Property, Plant, and Equipment, Excluding Deposits for Future Vessel Sales
The cash inflow from the sale of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale, excluding deposits for the future sales of vessels.
us-gaap_RelatedPartyTransactionRate
Related Party Transaction, Rate
Marketable security (losses) gains, net
us-gaap_MultiemployerPlanContributionsByEmployer
Multiemployer Plan, Contributions by Employer
Investments, at Equity, and Advances to 50% or Less Owned Companies
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures, Total
Equity in (Losses) Earnings of 50% or Less Owned Companies, Net of Tax
Equity losses, net
Equity in earnings (losses) of 50% or less owned companies
Accounts payable and accrued liabilities
Long-term Debt Obligation [Member]
Related to a long-term debt obligation.
us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
Loss Before Income Tax Benefit and Equity in Earnings of 50% or Less Owned Companies
Line of Credit [Member]
Income Tax Expense (Benefit)
Multiemployer Plan Name [Domain]
Gains (losses) on derivative instruments
Derivative gains (losses), net
Derivative losses (gains)
Multiemployer Plan Name [Axis]
Operating expenses
us-gaap_OperatingExpenses
Administrative and general
us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet
Debt Instrument, Increase (Decrease), Net, Total
Cash and cash equivalents
us-gaap_DebtInstrumentConvertibleConversionPrice1
Debt Instrument, Convertible, Conversion Price
us-gaap_DebtInstrumentConvertibleConversionRatio1
Debt Instrument, Convertible, Conversion Ratio
Amendment Flag
us-gaap_ComprehensiveIncomeNetOfTax
Comprehensive Loss attributable to SEACOR Marine Holdings Inc.
us-gaap_GainLossOnSaleOfBusiness
Gain (Loss) on Disposition of Business
New Accounting Pronouncements, Policy [Policy Text Block]
us-gaap_GainLossOnSaleOfPropertyPlantEquipment
Gain (Loss) on Disposition of Property Plant Equipment, Total
us-gaap_DebtInstrumentPeriodicPaymentPrincipal
Debt Instrument, Periodic Payment, Principal
us-gaap_TreasuryStockSharesAcquired
Treasury Stock, Shares, Acquired
us-gaap_IncreaseDecreaseInOtherOperatingAssets
Other assets
Current Fiscal Year End Date
us-gaap_DebtInstrumentInterestRateStatedPercentage
Debt Instrument, Interest Rate, Stated Percentage
us-gaap_DebtInstrumentInterestRateEffectivePercentage
Debt Instrument, Interest Rate, Effective Percentage
Basis of Accounting [Text Block]
Document Fiscal Period Focus
Document Fiscal Year Focus
Consolidation, Policy [Policy Text Block]
Document Period End Date
Entity Emerging Growth Company
Entity Ex Transition Period
us-gaap_DebtInstrumentFaceAmount
Debt Instrument, Face Amount
Document Type
Loss on Debt Extinguishment
Gain (Loss) on Extinguishment of Debt, Total
Interim Period, Costs Not Allocable [Domain]
Entity Small Business
Document Information [Line Items]
Document Information [Table]
Nature of Expense [Axis]
Entity Filer Category
Debt Instrument [Axis]
Entity Current Reporting Status
Debt Instrument, Name [Domain]
us-gaap_PercentageOfDebtHedgedByInterestRateDerivatives
Percentage of Debt Hedged by Interest Rate Derivatives
us-gaap_ImpairmentOfLongLivedAssetsHeldForUse
Impairment of Long-Lived Assets Held-for-use
Issuance of Warrants
us-gaap_IncreaseDecreaseInAccountsReceivable
Accounts receivables
Statement of Comprehensive Income [Abstract]
Entity Central Index Key
Entity Registrant Name
Entity [Domain]
Legal Entity [Axis]
us-gaap_AmortizationOfDeferredCharges
Amortization of deferred gains included in operating expenses as a reduction to rental expense
us-gaap_TreasuryStockValueAcquiredCostMethod
Treasury Stock, Value, Acquired, Cost Method
Restricted stock vesting
us-gaap_TreasuryStockValue
Shares held in treasury
Entity Common Stock, Shares Outstanding (in shares)
Long-term Debt [Text Block]
Trading Symbol
us-gaap_GainLossOnDispositionOfAssets
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property
Exercised (in shares)
us-gaap_TableTextBlock
Notes Tables
us-gaap_GainLossOnSaleOfOtherAssets
Gain from other sales
us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Line of Credit Facility, Maximum Borrowing Capacity
Exercise of options
Amortization of employee share awards
Related Party [Axis]
Related Party [Domain]
Bad debt expense
Granted (in shares)
us-gaap_WarrantsAndRightsOutstandingTerm
Warrants and Rights Outstanding, Term
Acquisition of consolidated joint venture
us-gaap_StockIssuedDuringPeriodSharesNewIssues
Stock Issued During Period, Shares, New Issues
Operating
Director share awards
us-gaap_StockIssuedDuringPeriodValueIssuedForServices
us-gaap_LiabilitiesAndStockholdersEquity
smhi_CommitmentToInvestAdditionalFundsIfCallByGeneralPartner
Commitment to Invest Additional Funds if Call By General Partner
Amount of commitment to invest additional funds in preferred equity if called by general partner.
us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance1
December 31, 2017 as adjusted
Reported Value Measurement [Member]
Issuance of Common Stock
Stock Issued During Period, Value, New Issues
UNITED STATES
Conversion option liability on Convertible Senior Notes
Retained earnings
Accumulated other comprehensive loss, net of tax
smhi_InvestmentInAffiliatesAmountOfPreferredEquityOffereingParticipated
Investment in Affiliates, Amount of Preferred Equity Offereing Participated
Amount of preferred equity offering participated
us-gaap_InterestExpense
Interest expense
Recently Adopted Accounting Standards [Policy Text Block]
Disclosure of accounting policy pertaining to recently adopted accounting standards.
Accrued capital, repair and maintenance expenditures
Carrying value as of the balance sheet date of obligations incurred through that date and payable for capital, repair and maintenance expenditures. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).
Changes in Operating Assets and Liabilities:
Deferred financing costs amortization
us-gaap_DisclosureTextBlockAbstract
Notes to Financial Statements
Convertible Senior Notes Converted to Warrants [Member]
Represents the conversion of convertible senior notes to warrants.
Derivative Instruments and Hedging Activities Disclosure [Text Block]
Other adjustments
The amount of other adjustment to deferred gain on sale of property.
Falcon Global Holdings [Member]
Represents Falcon Global Holdings, a subsidiary of the company.
Subsequent Event [Member]
FGUSA Credit Facility [Member]
Represents the credit agreement entered by FGUSA who is a wholly-owned subsidiary of FGH.
us-gaap_OperatingLeaseLiability
Operating Lease, Liability, Total
Pound Sterling Debt [Member]
Represents the debt borrowed in pound sterling.
Euro Debt [Member]
Represents the debt borrowed in Euro.
Subsequent Event Type [Axis]
Subsequent Event Type [Domain]
Pension and Other Postretirement Benefits Disclosure [Text Block]
Subsequent Events [Text Block]
us-gaap_OperatingLeaseRightOfUseAsset
Operating Lease, Right-of-Use Asset
Deferred income taxes
smhi_PropertyAndEquipmentMeasurementInput
Property and Equipment, Measurement Input
Value of input used to measure fair value of property and equipment.
Measurement Input Type [Axis]
Measurement Input Type [Domain]
Warrants Issued in Private Placement [Member]
Represents the warrants issued in a private placement.
Economic Obsolesence Factor [Member]
Measurement input using economic obsolescence factor.
Foreign taxes not creditable against U.S. income tax
smhi_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxNotCreditablePercent
Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to foreign income taxes that not creditable against demotic income tax.
smhi_JointVentureContributionFromNoncontrollingInterest
Joint Venture, Contribution from Noncontrolling Interest
The amount of contribution from noncontrolling interest shareholders.
smhi_JointVentureTotalCapital
Joint Venture, Total Capital
The total capital contributed by parent and noncontrolling interest shareholders to the joint venture.
Restricted stock amortization
Other Assets
us-gaap_DebtConversionConvertedInstrumentSharesIssued1
Debt Conversion, Converted Instrument, Shares Issued
Earnings Per Share, Policy [Policy Text Block]
us-gaap_DebtConversionOriginalDebtAmount1
Debt Conversion, Original Debt, Amount
Debt Conversion Description [Axis]
Debt Conversion, Name [Domain]
Comprehensive Income, Policy [Policy Text Block]
smhi_JointVentureContributionFromPreviousJointVenture
Joint Venture, Contribution from Previous Joint Venture
The amount of contribution from previous joint venture.
Debt discount amortization
Income Tax, Policy [Policy Text Block]
Property and equipment
us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
Depreciation and amortization
Gains (Losses) on Asset Dispositions and Impairments, Net
Loss from equipment sales, retirements or impairments
Africa [Member]
us-gaap_AssetsCurrent
Total current assets
Cash, cash equivalents and restricted cash
Stockholders' Equity Note Disclosure [Text Block]
us-gaap_AssetsNet
Net Assets, Ending Balance
Common stock, $.01 par value, 60,000,000 shares authorized; 20,441,590 and 17,675,356 shares issued in 2018 and 2017, respectively
Measurement Frequency [Axis]
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Fair Value, Measurement Frequency [Domain]
Fair Value, Measurements, Recurring [Member]
Common stock, shares authorized (in shares)
Common stock, shares issued (in shares)
Common stock, par value (in dollars per share)
Common Stock, Par or Stated Value Per Share
Restatement [Axis]
Restatement [Domain]
Previously Reported [Member]
Restatement Adjustment [Member]
Range [Domain]
Maximum [Member]
Minimum [Member]
us-gaap_PaymentsForPurchaseOfSecuritiesOperatingActivities
Gains from sale of marketable securities, net
Ownership [Domain]
Product and Service [Axis]
Product and Service [Domain]
Range [Axis]
Investment, Name [Domain]
Ownership [Axis]
Investment, Name [Axis]
Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block]
Property, Plant and Equipment Disclosure [Text Block]
Geographical [Axis]
Property, Plant and Equipment [Table Text Block]
Geographical [Domain]
Europe [Member]
Inventories
Portion at Fair Value Measurement [Member] [Default]
Estimate of Fair Value Measurement [Member]
Two Customers [Member]
Related to two customers.
Operating Revenues
Measurement Basis [Axis]
SEACOR Marlin LLC [Member]
Related to the entity SEACOR Marlin LLC.
Proceeds from sale of securities
Fair Value, Inputs, Level 3 [Member]
smhi_EquityMethodInvestmentOwnershipPercentSold
Equity Method Investment, Ownership, Percent Sold
The percentage ownership of equity method investments that was sold during the period.
Foreign currency losses, net
Currency loss
Other DNB Credit Facilities [Member]
Related to the other DNB credit facilities.
Fair Value Hierarchy and NAV [Domain]
Customer [Axis]
Loan Facility With DNB Bank ASA [Member]
Related to the loan facility with DNB Bank ASA.
Customer [Domain]
Term Loan to Acquire Two Vessels [Member]
Related to a term loan to acquire two vessels.
Fair Value, Inputs, Level 1 [Member]
Lease Obligation [Member]
Related to a lease obligation.
Fair Value, Inputs, Level 2 [Member]
Debt With Seacor 88 and Seacor 888 [Member]
Related to debt with Seacor 88 and Seacor 888.
Return to provision adjustment
Percentage of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operations, attributable to provision adjustments.
smhi_IncreaseDecreaseInTransitionTaxLiability
Increase (Decrease) in Transition Tax Liability
The amount of increase (decrease) in transition tax liability.
Fair Value Hierarchy and NAV [Axis]
Dividends received from equity investees
us-gaap_IncreaseDecreaseInCustomerDeposits
Increase (Decrease) in Customer Deposits
Estimated useful life (Year)
Property, Plant and Equipment, Useful Life
Noncontrolling interests in subsidiaries
Noncontrolling interest
Cash Flows from Operating Activities
Schedule of Segment Reporting Information, by Segment [Table Text Block]
Revenue Recognition, Policy [Policy Text Block]
Statement [Line Items]
Trade receivables, allowance for doubtful accounts
Trade, net of allowance for doubtful accounts of $4,077 and $4,039 in 2018 and 2017, respectively
Additional paid-in capital
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
AOCI Attributable to Parent [Member]
Partner Type of Partners' Capital Account, Name [Domain]
SEACOR Marine Holdings Inc. stockholders’ equity:
General Partner [Member]
Property, Plant and Equipment, Policy [Policy Text Block]
Other, net
Property, Plant and Equipment, Type [Axis]
us-gaap_NonoperatingIncomeExpense
Property, Plant and Equipment, Type [Domain]
Partner Type [Axis]
Segment Reporting Disclosure [Text Block]
Current Assets:
Fair Value Disclosures [Text Block]
Fair Value, by Balance Sheet Grouping [Table Text Block]
us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations
Cash, Restricted Cash and Cash Equivalents, Beginning of Period
Cash, Restricted Cash and Cash Equivalents, End of Period
Private Placement [Member]
Effects of Exchange Rate Changes on Cash and Cash Equivalents
Interest income
us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect
Net (Decrease) Increase in Cash, Cash Equivalents and Restricted Cash
us-gaap_Liabilities
Total liabilities
us-gaap_NetCashProvidedByUsedInFinancingActivities
Net cash provided by (used in) financing activities
Sale of Stock [Axis]
Sale of Stock [Domain]
Operating Loss
Operating Loss
invest_DerivativeNotionalAmount
Derivative, Notional Amount
us-gaap_NetCashProvidedByUsedInOperatingActivities
Net cash (used in) provided by operating activities
Other Income (Expense):
Prepaid expenses and other
us-gaap_NetCashProvidedByUsedInInvestingActivities
Net cash used in investing activities
Direct Vessel Profit
Direct Costs and Expenses
Counterparty Name [Axis]
Counterparty Name [Domain]
Schedule of Stockholders' Equity Note, Warrants or Rights [Table Text Block]
us-gaap_SaleLeasebackTransactionCurrentPeriodGainRecognized
Amortization of deferred gains against charter expense
us-gaap_ContractWithCustomerLiability
Contract with Customer, Liability, Total
Balance at beginning of period
Balance at end of period
Return of investments and advances from 50% or less owned companies
The cash inflow from investments 50% or less owned due to distributions classified as return of capital.
Derivative liabilities
us-gaap_InterestPayableCurrentAndNoncurrent
Interest Payable
SMHI Restricted Stock
us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment
Equity Method Investment, Other than Temporary Impairment
Consolidated Entities [Axis]
Consolidated Entities [Domain]
us-gaap_LettersOfCreditOutstandingAmount
Letters of Credit Outstanding, Amount
Equity Method Investments and Joint Ventures Disclosure [Text Block]
Equity Method Investments [Table Text Block]
us-gaap_CostsAndExpenses
Accumulated Gain (Loss), Net, Cash Flow Hedge, Noncontrolling Interest [Member]
Accumulated Foreign Currency Adjustment Attributable to Noncontrolling Interest [Member]
Geographic Distribution, Domestic [Member]
Noncontrolling Interest [Member]
Geographic Distribution, Foreign [Member]
Costs and Expenses:
Issuance of Warrants
us-gaap_ProceedsFromIssuanceOfWarrants
Geographic Distribution [Axis]
Geographic Distribution [Domain]
Retained Earnings [Member]
us-gaap_ProceedsFromIssuanceOfPrivatePlacement
Proceeds from Issuance of Private Placement
Equity Method Investments [Member]
Primary financial statement caption encompassing equity method investments.
Wind Farm Utility Vessel [Member]
Information pertaining to the wind farm utility vessel.
Issuance of stock
Convertible Senior Notes 3.75% [Member]
Information pertaining to the 3.75% Convertible Senior Notes.
Treasury Stock [Member]
Fast Support Vessels Previously Retired [Member]
Related to fast support vessels previously retired and removed from service.
Offshore Support Vessels [Member]
Information pertaining to the offshore support vessels.
Additional Paid-in Capital [Member]
us-gaap_DeferredGainOnSaleOfProperty
Balance at beginning of period
Balance at end of period
Common Stock [Member]
smhi_EarningsFromGoodsAndServicesSold
Direct Costs and Expenses
Amount of earnings from satisfaction of performance obligation by transferring promised good or service to customer.
Equity Components [Axis]
Equity Component [Domain]
us-gaap_LongTermDebt
Long-term Debt, Total
us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
Class of Warrant or Right, Exercise Price of Warrants or Rights
Balance (in dollars per share)
Balance (in dollars per share)
Class of Warrant or Right [Axis]
Class of Warrant or Right [Domain]
us-gaap_ClassOfWarrantOrRightOutstanding
Class of Warrant or Right, Outstanding
Balance, weighted average exercise price (in shares)
Balance, weighted average exercise price (in shares)
smhi_PaymentsForProceedsFromDerivativeInstrumentsOperatingActivities
Cash settlement on derivative transactions, net
The net amount of cash paid for or received to settle derivatives during the period not designated as hedges.
Issuance of noncontrolling interests
Amount of increase (decrease) to additional paid in capital (APIC) resulting from a true-up of non-controlling interests.
us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
Class of Warrant or Right, Number of Securities Called by Warrants or Rights
smhi_NumberOfEquipmentAcquired
Number of Equipment Acquired
Represents the number of of equipment acquired.
smhi_NumberOfEquipmentSold
Number of Equipment Sold
Represents the number of equipment sold.
Schedule of Deferred Gain [Table Text Block]
Tabular disclosure of schedule of deferred gains during the period.
Liftboats [Member]
Information pertaining to liftboats.
Anchor Handling Towing Supply [Member]
Information pertaining to anchor handling towing supply.
Fast Support Vessels [Member]
Information pertaining to fast support vessels.
smhi_ProceedsFromSaleOfPropertyPlantAndEquipmentIncludingDeposits
Proceeds from Sale of Property, Plant, and Equipment, Including Deposits
The cash inflow from the sale of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale, including deposits.
Deferred Revenue, by Arrangement, Disclosure [Table Text Block]
smhi_ProceedsFromDeposits
Proceeds from Deposits
Amount of cash inflow for receipts of deposits.
smhi_PaymentsToAcquirePropertyPlantAndEquipmentIncludingFairValueHedges
Payments to Acquire Property, Plant, and Equipment, Including Fair Value Hedges
The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets, including fair value hedges.
Falcon Global [Member]
Information pertaining to Falcon Global.
Revenues deferred during the period
Sea-Cat Crewzer II [Member]
Information pertaining to Sea-Cat Crewzer II.
us-gaap_DeferredRevenueRevenueRecognized1
Revenues recognized during the period
smhi_NumberOfEquipmentOperated
Number of Equipment Operated
Represents the number of equipment operated.
us-gaap_ConvertibleDebt
Convertible Debt, Total
Other Comprehensive Loss:
MexMar [Member]
Information pertaining to MexMar.
SEACOR Holdings [Member]
Information pertaining to SEACOR Holdings.
Sea-Cat Crewzer [Member]
Information pertaining to Sea-Cat Crewzer.
Windcat Workboats [Member]
Information pertaining to Windcat Workboats.
Supply Vessels [Member]
Information pertaining to supply vessels.
us-gaap_RepaymentsOfLongTermDebt
Repayments of Long-term Debt, Total
Payments on long-term debt
Other Noncontrolling Interests [Member]
Information pertaining to other noncontrolling interests.
Construction reserve funds
Fair value portion of construction reserve funds.
Schedule of Noncontrolling Interest [Table Text Block]
Tabular disclosure of noncontrolling interest.
smhi_AllocableShareOfUncalledCapital
Allocable Share of Uncalled Capital
Represents the entity's allocable share of uncalled capital.
Other Offshore Marine Services Joint Ventures [Member]
Information pertaining to other offshore marine services joint ventures.
OSV Partners [Member]
Information pertaining to OSV Partners.
us-gaap_DebtInstrumentUnamortizedDiscount
Debt Instrument, Unamortized Discount, Total
Accounting Policies [Abstract]
us-gaap_PartnersCapitalAccountContributions
Partners' Capital Account, Contributions
smhi_OtherLaborAndPerformanceGuarantee
Other Labor and Performance Guarantee
Represents the amount of other labor and performance guarantees.
us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption
Cumulative Effect of New Accounting Principle in Period of Adoption
Impact of adoption of accounting principle
Interest Expense [Member]
us-gaap_ProceedsFromIssuanceOfLongTermDebt
Proceeds from Issuance of Long-term Debt, Total
Brazil, Mexico, Central and South America [Member]
Information pertaining to Brazil, Mexico, Central and South America.
Time Charter [Member]
Information pertaining to time charter.
Middle East and Asia [Member]
Information pertaining to Middle East and Asia.
Personnel [Member]
Information pertaining to personnel services.
Repairs and Maintenance [Member]
Information pertaining to repairs and maintenance services.
Income Statement Location [Axis]
Bareboat Charter [Member]
Information pertaining to bareboat charter.
Income Statement Location [Domain]
Other Marine Services [Member]
Information pertaining to other marine services.
Fuel, Lubes and Supplies [Member]
Information pertaining to fuel, lubes and supplies.
Other Direct Costs and Expenses [Member]
Information pertaining to other direct costs and expenses.
Drydocking [Member]
Information pertaining to drydocking services.
Insurance and Loss Reserves [Member]
Information pertaining to insurance and loss reserves.
Leased-in Equipment [Member]
Information pertaining leased-in equipment.
Noncontrolling interest percent
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners
smhi_IncomeLossFromContinuingOperationsBeforeEquityMethodInvestmentsAndNoncontrollingInterestAfterTax
Loss Before Equity in Earnings of 50% or Less Owned Companies
Amount of income (loss) from continuing operations before income (loss) from equity method investments and income (loss) attributable to noncontrolling interest, but after tax of income (loss) from continuing operations.
us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted
Weighted Average Number of Shares Outstanding, Basic and Diluted
us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount
us-gaap_RepaymentsOfLinesOfCredit
Repayments of Lines of Credit
Diluted (in shares)
us-gaap_EarningsPerShareBasicAndDiluted
Earnings Per Share, Basic and Diluted, Total
us-gaap_OperatingLossCarryforwards
Operating Loss Carryforwards, Total
Scenario, Forecast [Member]
us-gaap_ProceedsFromLinesOfCredit
Proceeds from Lines of Credit, Total
Due to SEACOR Holdings
smhi_PropertyPlantAndEquipmentExcludingConstructionInProgress
Amount after accumulated depreciation, depletion and amortization of physical assets, excluding construction in progress, used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.
Construction Reserve Funds
Amount of construction reserve funds as of the balance sheet date.
Statement [Table]
Scenario [Axis]
us-gaap_MinorityInterestOwnershipPercentageByParent
Noncontrolling Interest, Ownership Percentage by Parent
Statement of Financial Position [Abstract]
Scenario, Unspecified [Domain]
Diluted Loss Per Common Share and Warrants of SEACOR Marine Holdings Inc. (in dollars per share)
Investments, at cost, in 50% or less owned companies (included in other assets)
smhi_IncreaseDecreaseInConstructionReserveFunds
Net change in construction reserve fund
The increase (decrease) during the reporting period in construction reserve funds
Basic (in shares)
Deferred Gains [Policy Text Block]
Disclosure of accounting policy for the deferral and amortization of gains on asset sales to 50% or less owned companies and gains on sale and leaseback transactions of significant deferred charges.
Other
us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments
smhi_ManagementFeeRelatedParty
SEACOR Holdings management fees
Amount of managements fees attributable to a related party.
us-gaap_EffectiveIncomeTaxRateContinuingOperations
Effective Income Tax Rate Reconciliation, Percent, Total
Noncontrolling Interest Disclosure [Text Block]
smhi_GuranteeFeesRelatedParty
SEACOR Holdings guarantee fees
Amount of guarantee fees attributable to a related party.
Basic Loss Per Common Share and Warrants of SEACOR Marine Holdings Inc. (in dollars per share)
Statement of Cash Flows [Abstract]
us-gaap_EffectiveIncomeTaxRateReconciliationTaxExemptIncome
Foreign earnings not subject to U.S. income tax
Statement of Stockholders' Equity [Abstract]
us-gaap_EffectiveIncomeTaxRateReconciliationMinorityInterestIncomeExpense
Noncontrolling interests
Income Statement [Abstract]
Unrecognized tax benefit
us-gaap_EffectiveIncomeTaxRateReconciliationTaxContingencies
Equity and Cost Method Investments, Policy [Policy Text Block]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Table Text Block]
Cash Flows from Financing Activities:
us-gaap_UnrecordedUnconditionalPurchaseObligationMaximumQuantity
Unrecorded Unconditional Purchase Obligation, Maximum Quantity
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]
Statutory rate
us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
Deferred Gains and Other Liabilities
Reclassification of derivative (gains) losses on cash flow hedges to interest expense
Reclassification of derivative losses on cash flow hedges
Principal payments on notes due from equity investees
Conversion Revolving Credit Facility from Windcat Workboats [Member]
Information pertaining to the conversion of revolving credit facility from Windcat Workboats.
us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount
Unrecorded Unconditional Purchase Obligation, Total
Capital distributions from equity investees
us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax
Derivative (losses) gains on cash flow hedges
Deferred Income Taxes
us-gaap_PaymentsForProceedsFromHedgeInvestingActivities
Cash settlements on derivative transactions, net
us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFourthAnniversary
Unrecorded Unconditional Purchase Obligation, Due within Four Years
Conversion Option Liability on Convertible Senior Notes
us-gaap_UnrecordedUnconditionalPurchaseObligationDueInRemainderOfFiscalYear
Unrecorded Unconditional Purchase Obligation, Due in Remainder of Fiscal Year
smhi_DebtAgreementMaximumBorrowingCapacity
Debt Agreement, Maximum Borrowing Capacity
Maximum borrowing capacity under a debt agreement on the amount that could be borrowed with a combination of, but not limited to, a line of credit and term loan.
Falcon Global USA LLC [Member]
Information pertaining to Falcon Global USA LLC.
us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnSecondAnniversary
Unrecorded Unconditional Purchase Obligation, Due within Two Years
us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnThirdAnniversary
Unrecorded Unconditional Purchase Obligation, Due within Three Years
smhi_PaymentsForDebtorInPossessionObligations
Payments for Debtor-in-possession Obligations
Amount of cash outflow for debtor-in-possession obligations.
Term Loan [Member]
Information pertaining to the term loan.
Foreign currency translation (losses) gains
Proceeds from sale of investment in equity investees
Sale of subsidiary joint venture
Proceeds from Divestiture of Interest in Joint Venture
Standby Safety Vessels [Member]
Information pertaining to standby safety vessels.
Carlyle Group [Member]
Information pertaining to Carlyle Group.
us-gaap_PaymentsToAcquireInterestInSubsidiariesAndAffiliates
Payments to Acquire Interest in Subsidiaries and Affiliates, Total
us-gaap_StockholdersEquity
us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired
Business acquisitions, net of cash acquired
us-gaap_PaymentsToAcquireAdditionalInterestInSubsidiaries
Purchase of subsidiary shares from noncontrolling interests
us-gaap_PaymentsToAcquireEquityMethodInvestments
Investments in and advances to 50% or less owned companies
smhi_CapitalCall
Capital Call
Represents the amount of capital call.
SeaCosco Offshore LLC [Member]
Information pertaining to SeaCosco Offshore LLC.
Class of Stock [Axis]
Long-Term Debt
Cash assumed on consolidation of 50% or less owned companies
Comprehensive Income (Loss) [Table Text Block]
Grant DIS [Member]
Information pertaining to Grant DIS.
Interest Rate Swap [Member]
us-gaap_PaymentsToAcquireLoansReceivable
Payments to Acquire Loans Receivable
us-gaap_DerivativeFixedInterestRate
Derivative, Fixed Interest Rate
Foreign Exchange Option [Member]
Other