CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net (loss) income	$ (2,678)	$ 178	$ 36
Other comprehensive (loss) income, net of tax:
(Loss) gain on derivatives	(38)	23	39
Actuarial pension gains	6
Foreign currency translation	(24)	(7)	(12)
Total comprehensive (loss) income	(2,734)	194	63
Less: Comprehensive (loss) income attributable to noncontrolling interests	9	(1)	2
Comprehensive (loss) income attributable to McDermott	$ (2,743)	$ 195	$ 61