CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (1,372)	$ (57)
Other comprehensive loss from continuing operations, net of tax:
Loss on derivatives	(42)	(19)
Foreign currency translation	(28)	(22)
Other comprehensive loss from discontinued operations, net of tax:
Foreign currency translation	(4)	(17)
Total comprehensive loss	(1,446)	(115)
Less: Comprehensive income (loss) attributable to noncontrolling interests	6	(1)
Comprehensive loss attributable to McDermott	$ (1,452)	$ (114)