Computation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data	3 Months Ended			6 Months Ended
	Jun. 30, 2011		Jun. 30, 2010	Jun. 30, 2011		Jun. 30, 2010
Basic:
Income from continuing operations less noncontrolling interests	$ 63,718		$ 78,691	$ 132,476		$ 130,253
Income (loss) from discontinued operations, net of tax	3,610		(2,657)	5,272		5,722
Net income attributable to McDermott International, Inc.	67,328		76,034	137,748		135,975
Weighted average common shares	234,573,031		231,847,145	234,207,053		231,335,723
Income from continuing operations less noncontrolling interests	$ 0.27		$ 0.34	$ 0.57		$ 0.56
Income (loss) from discontinued operations, net of tax	$ 0.02		$ (0.01)	$ 0.02		$ 0.02
Net income attributable to McDermott International, Inc.	$ 0.29		$ 0.33	$ 0.59		$ 0.59
Diluted:
Income from continuing operations less noncontrolling interests	63,718		78,691	132,476		130,253
Income (loss) from discontinued operations, net of tax	3,610		(2,657)	5,272		5,722
Net income attributable to McDermott International, Inc.	$ 67,328		$ 76,034	$ 137,748		$ 135,975
Weighted average common shares (basic)	234,573,031		231,847,145	234,207,053		231,335,723
Effect of dilutive securities:
Stock options, restricted stock and restricted stock units	2,971,643	[1]	2,576,401	2,938,073	[1]	3,252,568
Adjusted weighted average common shares and assumed exercises of stock options and vesting of stock awards	237,544,674		234,423,546	237,145,126		234,588,291
Income from continuing operations less noncontrolling interests	$ 0.27		$ 0.34	$ 0.56		$ 0.56
Income (loss) from discontinued operations, net of tax	$ 0.02		$ (0.01)	$ 0.02		$ 0.02
Net income attributable to McDermott International, Inc.	$ 0.28		$ 0.32	$ 0.58		$ 0.58

[1] Approximately 422,000 and 417,000 shares underlying outstanding stock-based awards were excluded from the computation of diluted earnings per share because they were antidilutive for the three-month and six-month periods ended June 30, 2011.