Business Combination - Schedule of Purchase Consideration (Detail) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended
	May 10, 2018	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Business Acquisition [Line Items]
Equity Combination consideration transferred		$ 31	$ 1,688
Total Combination consideration transferred, net of cash acquired	$ 4,100			$ 7	$ 2,374
Chicago Bridge & Iron Company N.V. [Member]
Business Acquisition [Line Items]
CB&I shares for Combination consideration	103
Business combination, number of McDermott's shares entitled for each share of CB&I owned	85
McDermott stock price on May 10, 2018	$ 19.92
Equity Combination consideration transferred	$ 1,684
Fair value of converted awards earned prior to the Combination	9
Total equity Combination consideration transferred	1,693
Cash consideration transferred	2,872
Total Combination consideration transferred	4,565
Less: Cash acquired	(498)
Total Combination consideration transferred, net of cash acquired	$ 4,067