Business Segment Information - Financial Data By Business Segment (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Revenue	$ 515,036	$ 446,176	$ 625,539	$ 961,212	$ 1,233,883
Income from Operations	9,390	(150)	38,380	9,240	86,479
Depreciation and amortization	53,304	53,663	59,979	106,967	119,760
Oil And Gas [Member]
Segment Reporting Information [Line Items]
Revenue	412,062	360,275	543,064	772,337	1,084,519
Income from Operations	27,683	19,862	52,573	47,545	127,423
Depreciation and amortization	51,382	51,768	58,174	103,150	116,097
ROVs [Member]
Segment Reporting Information [Line Items]
Revenue	103,432	94,022	139,641	197,454	287,262
Income from Operations	10,376	5,925	18,020	16,301	45,007
Depreciation and amortization	29,036	29,229	34,026	58,265	67,710
Subsea Products Member
Segment Reporting Information [Line Items]
Revenue	174,893	150,639	190,897	325,532	385,709
Income from Operations	10,552	11,483	25,121	22,035	65,761
Depreciation and amortization	12,785	12,999	12,952	25,784	25,759
Subsea Projects [Member]
Segment Reporting Information [Line Items]
Revenue	75,545	62,956	138,662	138,501	268,084
Income from Operations	3,000	187	10,237	3,187	17,026
Depreciation and amortization	7,781	8,080	8,353	15,861	16,872
Asset Integrity [Member]
Segment Reporting Information [Line Items]
Revenue	58,192	52,658	73,864	110,850	143,464
Income from Operations	3,755	2,267	(805)	6,022	(371)
Depreciation and amortization	1,780	1,460	2,843	3,240	5,756
Advanced Technologies [Member]
Segment Reporting Information [Line Items]
Revenue	102,974	85,901	82,475	188,875	149,364
Income from Operations	7,632	5,026	5,528	12,658	6,121
Depreciation and amortization	784	797	806	1,581	1,540
Unallocated Expenses [Member]
Segment Reporting Information [Line Items]
Income from Operations	(25,925)	(25,038)	(19,721)	(50,963)	(47,065)
Depreciation and amortization	$ 1,138	$ 1,098	$ 999	$ 2,236	$ 2,123