CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net (loss) income	$ (114)	$ 45	$ (171)	$ 79
Other comprehensive (loss) income, net of tax:
Loss on derivatives	(21)	(12)	(40)	(12)
Foreign currency translation	5	(11)	(34)	(12)
Total comprehensive (loss) income	(130)	22	(245)	55
Less: Comprehensive income (loss) attributable to noncontrolling interests	18	(2)	17	(3)
Comprehensive (loss) income attributable to McDermott	$ (148)	$ 24	$ (262)	$ 58