CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Revenues	$ 607,818	$ 519,431
Costs and Expenses:
Cost of operations	475,711	428,590
Research and development expenses	458	480
Selling, general and administrative expenses	48,934	36,533
Other operating (income) expenses, net	14,276	(2,211)
Operating income	68,439	56,039
Other expense:
Interest expense, net	(11,608)	(17,706)
Other non-operating income, net	1,719	560
Income before provision for income taxes	58,550	38,893
Provision for income taxes	20,715	10,771
Income before loss from Investments in Unconsolidated Affiliates	37,835	28,122
Loss from Investments in Unconsolidated Affiliates	(3,713)	(3,927)
Net income	34,122	24,195
Less: Net income (loss) attributable to noncontrolling interest	(1,067)	2,279
Net income attributable to McDermott	$ 35,189	$ 21,916
Net income per share attributable to McDermott
Basic	$ 0.12	$ 0.09
Diluted	$ 0.12	$ 0.08
Shares used in the computation of net income per share:
Basic	284,658,938	241,829,988
Diluted	285,050,524	282,285,595