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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net income (loss) attributable to McDermott International, Inc.	$ 3,666	$ (30,252)	$ 685	$ (84,169)
Weighted average common shares (basic)	238,594,178	237,429,394	238,128,962	237,262,044
Effect of dilutive securities:
Tangible equity units	40,896,300		40,896,300
Stock options, restricted stock and restricted stock units	1,306,677
Adjusted weighted average common shares and assumed exercises of stock options and vesting of stock awards (diluted)	280,797,155	237,429,394	279,025,262	237,262,044
Basic loss per share
Net income (loss) attributable to McDermott International, Inc.	$ 0.02	$ (0.13)		$ (0.35)
Diluted loss per share:
Adjusted net income (loss) attributable to McDermott International, Inc.	$ 0.01	$ (0.13)		$ (0.35)