Nature of Operations and Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2021 USD ($) Segment Vessel shares	Dec. 31, 2020 USD ($) shares	Dec. 31, 2019 USD ($) shares	Jul. 23, 2021	Jun. 01, 2021	Dec. 02, 2019 USD ($)	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 20, 2018
Nature Of Operations And Accounting Policies [Line Items]
Number of reportable segments | Segment	4
Equity method investment, ownership percentage				50.00%	50.00%				49.00%
Contract with customer, liability	$ 321,000	$ 3,307,000	$ 4,755,000					$ 1,327,000
Inventory reserves	0	0	0
Net book value	707,987,000	721,335,000	590,107,000
Capitalized interest costs, including allowance for funds used during construction, total	300,000	900,000	1,500,000
Impairment of long-lived assets held-for-use		18,800,000
Partial impairment of right to use assets		5,300,000
Equity method investment, other than temporary impairment	$ 0	$ 0	0
Deferred gain activity reclassed to retained earnings			11,000,000.0
Deferred gain on sale of property other adjustments			800,000
Deferred gain net			$ 0
Incremental common shares attributable to conversion of debt securities, total | shares	1,439,483	1,488,292	1,826,966
Right-of-use asset - operating leases	$ 6,608,000	$ 7,134,000
Operating Lease, Liability	6,871,000
Cumulative effect on retained earnings, net of tax	(22,907,000)	(51,839,000)
Deferred taxes	$ 67,261,000	$ 66,420,000
Change in Accounting Principle for Unamortized Deferred Gains
Nature Of Operations And Accounting Policies [Line Items]
Deferred gain net							$ 11,000.0
Deferred taxes							2,300
Accounting Standards Update 2016-02
Nature Of Operations And Accounting Policies [Line Items]
Right-of-use asset - operating leases							33,700,000
Operating Lease, Liability							31,900,000
Change in accounting principle, accounting standards update, adopted [true false]	true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2019
Change in accounting principle, accounting standards update, immaterial effect [true false]	false
Accounting Standards Update 2016-02 | Cumulative Effect, Period of Adoption, Adjustment | Change in Accounting Principle for Equipment, Office and Land Leases
Nature Of Operations And Accounting Policies [Line Items]
Cumulative effect on retained earnings, net of tax							1,700,000
Accounting Standards Update 2016-02 | Cumulative Effect, Period of Adoption, Adjustment | Change in Accounting Principle for Unamortized Deferred Gains
Nature Of Operations And Accounting Policies [Line Items]
Cumulative effect on retained earnings, net of tax							$ 8,700,000
Performance Share Awards
Nature Of Operations And Accounting Policies [Line Items]
Number of shares issued | shares	157,455	149,200	109,600
Number of shares outstanding | shares	354,964
Restricted Stock
Nature Of Operations And Accounting Policies [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount | shares	1,112,256	436,714	303,609
Dilutive securities included in computation of earnings per share, amount | shares	50,834
Employee Stock Option
Nature Of Operations And Accounting Policies [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount | shares	1,061,357	1,120,541	913,569
Continuing Operations
Nature Of Operations And Accounting Policies [Line Items]
Depreciation, total	$ 57,400,000	$ 57,200,000	$ 57,200,000
Discontinued Operations
Nature Of Operations And Accounting Policies [Line Items]
Depreciation, total	$ 0	6,200,000	6,800,000
Net book value						$ 24,300,000
Offshore Support Vessels
Nature Of Operations And Accounting Policies [Line Items]
Estimated useful life (Year)	20 years
ERRVs | Discontinued Operations
Nature Of Operations And Accounting Policies [Line Items]
Depreciation, total			3,500,000
Liftboat Vessels
Nature Of Operations And Accounting Policies [Line Items]
Additional impairment of right-to-use assets		7,000,000.0
Anchor Handling Towing Supply
Nature Of Operations And Accounting Policies [Line Items]
Additional impairment of right-to-use assets		500,000
Specialty Vessel
Nature Of Operations And Accounting Policies [Line Items]
Additional impairment of right-to-use assets		1,200,000
Vessel Under Construction
Nature Of Operations And Accounting Policies [Line Items]
Additional impairment of right-to-use assets		$ 4,800,000
Contract Completions and Certain Reclassifications
Nature Of Operations And Accounting Policies [Line Items]
Contract with customer, liability, revenue recognized	$ 1,500,000
Prepaid Vessel Management Fees
Nature Of Operations And Accounting Policies [Line Items]
Contract with customer, liability, revenue recognized	2,000,000.0
Geographic Distribution, Domestic | Prepaid Charter Modification And Reservation
Nature Of Operations And Accounting Policies [Line Items]
Contract with customer, liability	$ 300,000
Minimum
Nature Of Operations And Accounting Policies [Line Items]
Equity method investment, ownership percentage	20.00%
Minimum | SEACOR Marine Foreign Holdings
Nature Of Operations And Accounting Policies [Line Items]
Equity method investment, ownership percentage	50.00%
Maximum
Nature Of Operations And Accounting Policies [Line Items]
Equity method investment, ownership percentage	50.00%	50.00%
OVH
Nature Of Operations And Accounting Policies [Line Items]
Number of vessels owned | Vessel	4
CME
Nature Of Operations And Accounting Policies [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners	51.00%
Subsidiaries of CME
Nature Of Operations And Accounting Policies [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners	51.00%
MexMar
Nature Of Operations And Accounting Policies [Line Items]
Number of vessels owned | Vessel	16
Equity method investment, ownership percentage	49.00%
SMI
Nature Of Operations And Accounting Policies [Line Items]
Equity method investment, ownership percentage	49.00%
UNITED STATES
Nature Of Operations And Accounting Policies [Line Items]
Number of vessels | Vessel	15
Number of vessels owned | Vessel	12
Number of vessels leased-in | Vessel	2
Number of vessels managed-in | Vessel	1
Net book value	$ 125,879,000	$ 123,201,000	139,878,000
Africa and Europe
Nature Of Operations And Accounting Policies [Line Items]
Number of vessels | Vessel	16
Number of vessels owned | Vessel	15
Number of vessels leased-in | Vessel	1
Net book value	$ 151,219,000	194,512,000	189,527,000
Middle East and Asia
Nature Of Operations And Accounting Policies [Line Items]
Number of vessels | Vessel	20
Number of vessels owned | Vessel	20
Net book value	$ 254,543,000	286,165,000	219,407,000
Latin America
Nature Of Operations And Accounting Policies [Line Items]
Number of vessels | Vessel	30
Number of vessels owned | Vessel	10
Number of vessels joint ventured | Vessel	20
Net book value	$ 176,347,000	$ 117,457,000	$ 41,295,000