Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues:
Revenue	$ 92,401	$ 86,467	$ 265,858	$ 305,179
Costs and expenses:
Vessel operating costs	65,344	61,784	190,627	205,383
Costs of other operating revenues	355	219	2,003	3,063
General and administrative	18,045	17,438	50,875	56,455
Depreciation and amortization	27,980	30,777	86,256	86,028
Long-lived asset impairments	2,167	1,945	2,167	67,634
Affiliate credit loss impairment expense (credit)	0	0	(1,000)	53,581
Affiliate guarantee obligation	0	0	0	2,000
(Gain) loss on asset dispositions, net	74	(520)	2,954	(7,511)
Costs and Expenses, Total	113,965	111,643	333,882	466,633
Operating loss	(21,564)	(25,176)	(68,024)	(161,454)
Other income (expense):
Foreign exchange loss	(523)	(1,153)	(951)	(2,365)
Equity in net earnings (losses) of unconsolidated companies	100	0	(1,697)	0
Dividend income from unconsolidated company	0	0	0	17,150
Interest income and other, net	148	272	179	1,084
Interest and other debt costs, net	(3,681)	(6,071)	(12,166)	(18,172)
Nonoperating Income (Expense), Total	(3,956)	(6,952)	(14,635)	(2,303)
Loss before income taxes	(25,520)	(32,128)	(82,659)	(163,757)
Income tax expense	887	5,953	8,922	3,512
Net loss	(26,407)	(38,081)	(91,581)	(167,269)
Net loss attributable to noncontrolling interests	(149)	(154)	(546)	(274)
Net loss attributable to Tidewater Inc.	$ (26,258)	$ (37,927)	$ (91,035)	$ (166,995)
Basic loss per common share (in dollars per share)	$ (0.64)	$ (0.94)	$ (2.22)	$ (4.15)
Diluted loss per common share (in dollars per share)	$ (0.64)	$ (0.94)	$ (2.22)	$ (4.15)
Weighted average common shares outstanding (in shares)	41,132	40,405	40,918	40,271
Adjusted weighted average common shares (in shares)	41,132	40,405	40,918	40,271
Vessel [Member]
Revenues:
Revenue	$ 91,634	$ 85,395	$ 261,141	$ 298,344
Product and Service, Other [Member]
Revenues:
Revenue	$ 767	$ 1,072	$ 4,717	$ 6,835