Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income attributable to McDermott International, Inc.		$ 94,701	$ 16,108	$ 153,030	$ 34,593
Weighted average common stock (basic)		283,991,161	240,899,888	269,720,153	240,093,169
Effect of dilutive securities:
Tangible equity units	[1]		40,896,300	12,827,388	40,896,300
Stock options, restricted stock and restricted stock units		1,783,460	2,111,165	2,312,169	2,143,451
Potential dilutive common stock		285,774,621	283,907,353	284,859,710	283,132,920
Net income per share attributable to McDermott International, Inc.
Basic:		$ 0.33	$ 0.07	$ 0.57	$ 0.14
Diluted:		$ 0.33	$ 0.06	$ 0.54	$ 0.12

[1] Represents weighted average TEUs outstanding for the nine months periods ended September 30, 2017.