Business Segment Information - Summary Of Financial Data By Segment (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net revenues		$ 163,266	$ 163,260	$ 150,329	$ 104,528	$ 128,031	$ 161,245	$ 107,267	$ 91,039	$ 581,383	$ 487,582	$ 695,802
Income (loss) from operations										(1,130)	(63,235)	(307,360)
Net interest expense										18,778	31,239	26,914
Equity in losses of investments										(2,368)	(2,166)	(124,345)
Income (loss) before income taxes										(20,372)	(93,915)	(478,170)
Income tax provision (benefit)										(50,424)	(12,470)	(101,190)
Capital expenditures										231,127	186,487	320,311
Depreciation and amortization										108,745	114,187	120,401
Gain on disposition of assets, net										(39)	1,290	92
Asset impairment charges										0	0	345,010
Goodwill impairment charge										0	45,107	16,399
Unrealized losses on foreign exchange contracts										(4,423)	(8,800)	18,281
United Kingdom [Member]
Segment Reporting Information [Line Items]
Net revenues										156,000	123,600	187,700
Helix 534 [Member]
Segment Reporting Information [Line Items]
Gain on disposition of assets, net	$ 1,300
Asset impairment charges												205,200
Capitalized Vessel Project Costs [Member]
Segment Reporting Information [Line Items]
Impairment charges to write off capitalized costs												6,300
HP I [Member]
Segment Reporting Information [Line Items]
Asset impairment charges												133,400
Intercompany Elimination [Member]
Segment Reporting Information [Line Items]
Net revenues										(42,065)	(39,356)	(54,473)
Income (loss) from operations										884	(372)	(98)
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations										(40,630)	(39,384)	(33,866)
Income (loss) before income taxes										(54,853)	(70,890)	(55,475)
Income tax provision (benefit)										(17,550)	(26,146)	(19,423)
Capital expenditures										125	(199)	(135)
Corporate and Eliminations [Member]
Segment Reporting Information [Line Items]
Net interest expense										18,964	31,373	26,602
Depreciation and amortization										2,882	5,995	6,242
Well Intervention [Member] | United Kingdom [Member]
Segment Reporting Information [Line Items]
Goodwill impairment charge												16,400
Well Intervention [Member] | Helix 534 [Member]
Segment Reporting Information [Line Items]
Gain on disposition of assets, net	$ 1,300
Asset impairment charges												205,200
Well Intervention [Member] | Capitalized Vessel Project Costs [Member]
Segment Reporting Information [Line Items]
Impairment charges to write off capitalized costs												6,300
Well Intervention [Member] | Reportable Segments [Member]
Segment Reporting Information [Line Items]
Net revenues										406,341	294,000	373,301
Income (loss) from operations										52,733	14,910	(194,381)
Net interest expense										(156)	(109)	(102)
Income (loss) before income taxes										48,948	18,813	(193,572)
Income tax provision (benefit)										(29,934)	12,531	(1,230)
Capital expenditures										230,354	185,892	307,879
Depreciation and amortization										68,301	68,392	66,095
Well Intervention [Member] | Intercompany Elimination [Member]
Segment Reporting Information [Line Items]
Net revenues										(11,489)	(8,442)	(22,855)
Robotics [Member]
Segment Reporting Information [Line Items]
Goodwill impairment charge		$ 45,100									45,100
Unrealized losses on foreign exchange contracts												18,300
Robotics [Member] | Reportable Segments [Member]
Segment Reporting Information [Line Items]
Net revenues										152,755	160,580	301,026
Income (loss) from operations										(42,289)	(72,250)	27,832
Net interest expense										(30)	(25)	29
Income (loss) before income taxes										(40,271)	(73,533)	2,454
Income tax provision (benefit)										(11,972)	(9,948)	515
Capital expenditures										648	720	10,700
Depreciation and amortization										23,626	25,848	26,724
Robotics [Member] | Intercompany Elimination [Member]
Segment Reporting Information [Line Items]
Net revenues										(30,576)	(30,914)	(31,618)
Production Facilities [Member] | HP I [Member]
Segment Reporting Information [Line Items]
Asset impairment charges												133,400
Production Facilities [Member] | Reportable Segments [Member]
Segment Reporting Information [Line Items]
Net revenues										64,352	72,358	75,948
Income (loss) from operations										28,172	33,861	(106,847)
Net interest expense										0	0	385
Income (loss) before income taxes										25,804	31,695	(231,577)
Income tax provision (benefit)										9,032	11,093	(81,052)
Capital expenditures										0	74	1,867
Depreciation and amortization										$ 13,936	$ 13,952	$ 21,340