Consolidated Statements of Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Operating Revenues	$ 170,941	$ 141,837	$ 174,453
Costs and Expenses:
Operating	127,406	91,145	109,523
Administrative and general	37,639	40,051	39,791
Lease expense	6,085	7,525	15,840
Depreciation and amortization	57,395	57,167	57,166
Costs and Expenses	228,525	195,888	222,320
Gains (Losses) on Asset Dispositions and Impairments, Net	20,436	(17,588)	(6,461)
Operating Loss	(37,148)	(71,639)	(54,328)
Other Income (Expense):
Interest income	1,302	1,273	1,389
Interest expense	(28,111)	(30,691)	(28,956)
SEACOR Holdings guarantee fees	(7)	(47)	(108)
Gain on debt extinguishment	61,994
Derivative gains, net	391	4,310	71
Foreign currency losses, net	(1,235)	(1,294)	(2,541)
Gain (Loss) from return of investments in 50% or less owned companies and other, net	9,441	(19)	(1)
Nonoperating Income (Expense)	43,775	(26,468)	(30,146)
Income (Loss) from Continuing Operations Before Tax Expense (Benefit) and Equity in Earnings of 50% or Less Owned Companies	6,627	(98,107)	(84,474)
Income Tax Expense (Benefit):
Current	6,633	(25,182)	4,921
Deferred	4,860	2,258	(12,890)
Income Tax Expense (Benefit)	11,493	(22,924)	(7,969)
Loss Before Equity in Earnings of 50% or Less Owned Companies	(4,866)	(75,183)	(76,505)
Equity in Earnings Gains (Losses) of 50% or Less Owned Companies, Net of Tax	15,078	(8,163)	(14,459)
Income (Loss) from Continuing Operations	10,212	(83,346)	(90,964)
Income (Loss) on Discontinued Operations, Net of Tax (see Note 20)	22,925	364	(7,731)
Net Income (Loss)	33,137	(82,982)	(98,695)
Net Income (Loss) attributable to Noncontrolling Interests in Subsidiaries	1	(4,067)	(5,858)
Net Income (Loss) attributable to SEACOR Marine Holdings Inc.	$ 33,136	$ (78,915)	$ (92,837)
Net Earnings (Loss) Per Common Share from Continuing Operations:
Basic	$ 0.40	$ (3.20)	$ (3.62)
Diluted	0.40	(3.20)	(3.62)
Net Earnings (Loss) Per Share from Discontinued Operations:
Basic	0.90	0.02	(0.33)
Diluted	0.90	0.02	(0.33)
Net Earnings (Loss) per Share:
Basic	1.30	(3.18)	(3.95)
Diluted	$ 1.30	$ (3.18)	$ (3.95)
Weighted Average Common Shares and Warrants Outstanding:
Basic	25,444,693	24,785,744	23,513,925
Diluted	25,495,527	24,785,744	23,513,925