Business Segment Information - Financial Data By Business Segment (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Revenue	$ 519,300	$ 478,674	$ 476,120	$ 1,414,387	$ 1,437,332
Income from Operations	(1,552)	(19,637)	10,531	(48,338)	19,771
Depreciation and amortization	50,703	59,843	53,513	164,674	160,480
Oil And Gas [Member]
Segment Reporting Information [Line Items]
Revenue	409,462	374,588	389,414	1,114,480	1,161,751
Income from Operations	14,502	(164)	26,954	13,015	74,499
Depreciation and amortization	48,876	58,072	51,629	158,776	154,779
ROVs [Member]
Segment Reporting Information [Line Items]
Revenue	105,045	107,426	104,617	298,065	302,071
Income from Operations	772	4,542	5,009	2,916	21,310
Depreciation and amortization	27,428	28,269	28,269	83,339	86,534
Subsea Products Member
Segment Reporting Information [Line Items]
Revenue	137,099	121,704	143,583	385,491	469,115
Income from Operations	5,367	2,295	12,383	9,417	34,418
Depreciation and amortization	12,349	14,914	13,340	41,288	39,124
Subsea Projects [Member]
Segment Reporting Information [Line Items]
Revenue	104,972	78,036	80,116	239,868	218,617
Income from Operations	6,088	(10,358)	6,512	(6,629)	9,699
Depreciation and amortization	7,464	13,053	7,881	28,830	23,742
Asset Integrity [Member]
Segment Reporting Information [Line Items]
Revenue	62,346	67,422	61,098	191,056	171,948
Income from Operations	2,275	3,357	3,050	7,311	9,072
Depreciation and amortization	1,635	1,836	2,139	5,319	5,379
Advanced Technologies [Member]
Segment Reporting Information [Line Items]
Revenue	109,838	104,086	86,706	299,907	275,581
Income from Operations	8,960	7,886	6,602	18,514	19,260
Depreciation and amortization	792	737	796	2,295	2,377
Unallocated Expenses [Member]
Segment Reporting Information [Line Items]
Income from Operations	(25,014)	(27,359)	(23,025)	(79,867)	(73,988)
Depreciation and amortization	$ 1,035	$ 1,034	$ 1,088	$ 3,603	$ 3,324