CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income		$ 94	$ 79	$ 154
Other comprehensive (loss) income, net of tax:
(Loss) gain on derivatives	$ (1)	9	(13)	20
Foreign currency translation	(8)	(7)	(20)	(7)
Total comprehensive income	(9)	96	46	167
Less: Comprehensive (loss) income attributable to noncontrolling interests	(2)	(1)	(5)	1
Comprehensive (loss) income attributable to McDermott	$ (7)	$ 97	$ 51	$ 166