Business Segment Information - Financial Data By Business Segment (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Revenue	$ 476,120	$ 515,036	$ 549,275	$ 1,437,332	$ 1,783,158
Income from Operations	10,531	9,390	(11,856)	19,771	74,623
Depreciation and amortization	53,513	53,304	74,200	160,480	193,960
Oil And Gas [Member]
Segment Reporting Information [Line Items]
Revenue	389,414	412,062	466,570	1,161,751	1,551,089
Income from Operations	26,954	27,683	2,018	74,499	129,441
Depreciation and amortization	51,629	51,382	72,465	154,779	188,562
ROVs [Member]
Segment Reporting Information [Line Items]
Revenue	104,617	103,432	126,507	302,071	413,769
Income from Operations	5,009	10,376	(23,845)	21,310	21,162
Depreciation and amortization	28,269	29,036	43,705	86,534	111,415
Subsea Products Member
Segment Reporting Information [Line Items]
Revenue	143,583	174,893	157,269	469,115	542,978
Income from Operations	12,383	10,552	6,109	34,418	71,870
Depreciation and amortization	13,340	12,785	14,205	39,124	39,964
Subsea Projects [Member]
Segment Reporting Information [Line Items]
Revenue	80,116	75,545	110,799	218,617	378,883
Income from Operations	6,512	3,000	15,029	9,699	32,055
Depreciation and amortization	7,881	7,781	8,575	23,742	25,447
Asset Integrity [Member]
Segment Reporting Information [Line Items]
Revenue	61,098	58,192	71,995	171,948	215,459
Income from Operations	3,050	3,755	4,725	9,072	4,354
Depreciation and amortization	2,139	1,780	5,980	5,379	11,736
Advanced Technologies [Member]
Segment Reporting Information [Line Items]
Revenue	86,706	102,974	82,705	275,581	232,069
Income from Operations	6,602	7,632	4,357	19,260	10,478
Depreciation and amortization	796	784	789	2,377	2,329
Unallocated Expenses [Member]
Segment Reporting Information [Line Items]
Income from Operations	(23,025)	(25,925)	(18,231)	(73,988)	(65,296)
Depreciation and amortization	$ 1,088	$ 1,138	$ 946	$ 3,324	$ 3,069