Operations by Business Segment and Geographic Area - Financial Data By Business Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenue	$ 1,921,507	$ 2,271,603	$ 3,062,754
Income from Operations	10,656	70,764	373,810
Depreciation, Depletion and Amortization, Nonproduction	213,519	250,247	241,235
Oil And Gas [Member]
Segment Reporting Information [Line Items]
Revenue	1,547,939	1,962,527	2,744,878
Income from Operations	89,415	143,158	478,368
Depreciation, Depletion and Amortization, Nonproduction	206,124	243,104	233,732
ROVs [Member]
Segment Reporting Information [Line Items]
Revenue	393,655	522,121	807,723
Income from Operations	22,366	25,193	192,514
Depreciation, Depletion and Amortization, Nonproduction	113,979	140,967	143,364
Subsea Products [Member]
Segment Reporting Information [Line Items]
Revenue	625,513	692,030	959,714
Income from Operations	45,539	75,938	175,585
Depreciation, Depletion and Amortization, Nonproduction	52,561	53,759	49,792
Subsea Projects [Member]
Segment Reporting Information [Line Items]
Revenue	291,993	472,979	604,484
Income from Operations	10,279	34,476	92,034
Depreciation, Depletion and Amortization, Nonproduction	31,869	34,042	29,863
Asset Integrity [Member]
Segment Reporting Information [Line Items]
Revenue	236,778	275,397	372,957
Income from Operations	11,231	7,551	18,235
Depreciation, Depletion and Amortization, Nonproduction	7,715	14,336	10,713
Advanced Technologies [Member]
Segment Reporting Information [Line Items]
Revenue	373,568	309,076	317,876
Income from Operations	22,039	11,809	9,689
Depreciation, Depletion and Amortization, Nonproduction	3,171	3,120	2,549
Unallocated Expenses [Member]
Segment Reporting Information [Line Items]
Income from Operations	(100,798)	(84,203)	(114,247)
Depreciation, Depletion and Amortization, Nonproduction	$ 4,224	$ 4,023	$ 4,954