CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 45	$ 36	$ 79	$ 60
Other comprehensive (loss) income, net of tax:
(Loss) gain on derivatives	(12)	9	(12)	11
Foreign currency translation	(11)		(12)
Total comprehensive income	22	45	55	71
Less: Comprehensive (loss) income attributable to noncontrolling interests	(2)		(3)	2
Comprehensive income attributable to McDermott	$ 24	$ 45	$ 58	$ 69