Computation of Basic and Diluted Earnings Per Common Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Basic:
Income from continuing operations less noncontrolling interests	$ 59,261		$ 68,758
Income from discontinued operations, net of tax	3,497		1,662
Net Income Attributable to McDermott International, Inc.	$ 62,758		$ 70,420
Diluted:
Weighted average common shares (basic)	235,208,252		233,841,075
Effect of dilutive securities:
Stock options, restricted stock and restricted stock units	2,124,375	[1]	2,904,503	[1]
Adjusted weighted average common shares and assumed exercises of stock options and vesting of stock awards (diluted)	237,332,627		236,745,578
Basic earnings per share:
Income from continuing operations less noncontrolling interests	$ 0.25		$ 0.29
Income from discontinued operations, net of tax	$ 0.01		$ 0.01
Net income attributable to McDermott International, Inc.	$ 0.27		$ 0.30
Diluted earnings per share:
Income from continuing operations less noncontrolling interests	$ 0.25		$ 0.29
Income from discontinued operations, net of tax	$ 0.01		$ 0.01
Net income attributable to McDermott International, Inc.	$ 0.26		$ 0.30

[1] Approximately 1.8 million and 0.4 million shares underlying outstanding stock-based awards were excluded from the computation of diluted earnings per share because they were antidilutive for the three-month periods ended March 31, 2012 and 2011, respectively.