CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Revenues	[1]	$ 2,289	$ 959	$ 4,632	$ 2,267
Costs and Expenses:
Cost of operations		1,986	774	3,948	1,853
Project related intangibles amortization		30		42
Total cost of operations		2,016	774	3,990	1,853
Research and development expenses		8	2	13	3
Selling, general and administrative expenses		64	55	188	142
Other intangibles amortization		25		35
Transaction costs		5		45
Restructuring and integration costs		31		106
Other operating expenses (income), net		1		2	(2)
Total expenses		2,150	831	4,379	1,996
Income (loss) from investments in unconsolidated affiliates		3	(3)	2	(9)
Investment in unconsolidated affiliates-related amortization		(13)		(13)
Operating income		129	125	242	262
Other expense:
Interest expense, net		(86)	(12)	(169)	(51)
Other non-operating income (expense), net		1		(13)	(2)
Total other expense, net		(85)	(12)	(182)	(53)
Income before provision for income taxes		44	113	60	209
Income tax expense (benefit)		44	19	(19)	53
Non-operating loss from investments in unconsolidated affiliates					(2)
Net income			94	79	154
Less: Net (loss) income attributable to noncontrolling interests		(2)	(1)	(5)	1
Net income attributable to McDermott		$ 2	$ 95	$ 84	$ 153
Net income per share attributable to McDermott
Basic		$ 0.01	$ 1.00	$ 0.60	$ 1.70
Diluted		$ 0.01	$ 1.00	$ 0.60	$ 1.61
Shares used in the computation of net income per share:
Basic		180	95	140	90
Diluted		181	95	141	95

[1] Intercompany transactions were not significant for the three and nine months ended September 30, 2018 and 2017, respectively.