CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Revenues	[1]	$ 2,984,768	$ 2,635,983	$ 3,070,275
Costs and Expenses:
Cost of operations		2,449,443	2,249,270	2,690,560
Research and development expenses		4,946	346	724
Selling, general and administrative expenses		198,973	178,752	217,239
Other operating (income) expenses, net		7,204	65,362	49,070
Total costs and expenses		2,660,566	2,493,730	2,957,593
Operating income		324,202	142,253	112,682
Other expense:
Interest expense, net		(62,974)	(58,871)	(50,058)
Other non-operating income (expense), net		(1,069)	(1,067)	1,986
Total other expense, net		(64,043)	(59,938)	(48,072)
Income before provision for income taxes		260,159	82,315	64,610
Provision for income taxes		68,716	41,926	51,963
Income before loss from Investments in Unconsolidated Affiliates		191,443	40,389	12,647
Loss from Investments in Unconsolidated Affiliates		(14,228)	(4,090)	(21,486)
Net income (loss)		177,215	36,299	(8,839)
Less: Net income (loss) attributable to noncontrolling interest		(1,331)	2,182	9,144
Net income (loss) attributable to McDermott International, Inc.		$ 178,546	$ 34,117	$ (17,983)
Net income (loss) per share attributable to McDermott International, Inc.:
Basic		$ 0.65	$ 0.14	$ (0.08)
Diluted		$ 0.63	$ 0.12	$ (0.08)
Shares used in the computation of net income (loss) per share:
Basic		273,337,931	240,359,363	238,240,763
Diluted		285,634,757	284,184,239	238,240,763

[1] Intercompany transactions were not significant during 2017, 2016 and 2015.