Nature of Operations and Accounting Policies - Summary of Property and Equipment from Continuing Operations (Details) - USD ($) $ in Thousands		Dec. 31, 2021		Dec. 31, 2020		Dec. 31, 2019
Historical cost		$ 1,025,284	[1]	$ 1,012,873	[1]	$ 899,024
Accumulated depreciation		(317,297)		(291,538)		(308,917)
Net book value		707,987		721,335		$ 590,107
Offshore Support Vessels, Anchor Handling Towing Supply
Historical cost	[1],[2]	49,632		50,189
Accumulated depreciation	[2]	(33,200)		(31,779)
Net book value	[2]	16,432		18,410
Fast Support Vessels
Historical cost	[1],[3]	362,309		375,747
Accumulated depreciation	[3]	(116,878)		(104,739)
Net book value	[3]	245,431		271,008
Offshore Support Vessels, Supply
Historical cost	[1]	282,243		238,624
Accumulated depreciation		(20,613)		(15,991)
Net book value		261,630		222,633
Offshore Support Vessels, Specialty
Historical cost	[1]	3,163
Accumulated depreciation		(3,138)
Net book value		25
Offshore Support Vessels, Liftboats
Historical cost	[1]	301,992	[4]	321,751
Accumulated depreciation		(120,823)	[4]	(117,364)
Net book value		181,169	[4]	204,387
General Machinery and Spares
Historical cost	[1]	8,814		7,746
Accumulated depreciation		(8,463)		(7,733)
Net book value		351		13
Property, Plant and Equipment, Other Types
Historical cost	[1],[5]	17,131		15,653
Accumulated depreciation	[5]	(14,182)		(10,794)
Net book value	[5]	$ 2,949		4,859
Crew Transfer Vessels
Historical cost	[1]			3,163
Accumulated depreciation				(3,138)
Net book value				$ 25

[1] Includes property and equipment acquired in business acquisitions at acquisition date fair value, and net of the impact of recognized impairment charges.

[2] Anchor Handling Towing Supply (“AHTS”).

[3] Fast support vessels (“FSVs”)

[4] As of December 31, 2021, the Company classified a liftboat included in the United States, primarily Gulf of Mexico segment, with a carrying value of $0.3 million, as an asset held for sale. In January 2022, in the normal course of business, the Company sold the liftboat for net proceeds of $3.2 million in cash and recorded a gain of $2.7 million after transaction costs of $0.2 million.

[5] Includes land, buildings, leasehold improvements, vehicles and other property and equipment. As of December 31, 2021, the Company classified a building included in the Middle East and Asia segment, with a carrying value of $2.0 million, as held for sale. In January 2022, the Company sold the building for net proceeds of $2.4 million in cash and recorded a gain of $0.4 million.