Computation of Basic and Diluted Earnings Per Common Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Earnings Per Share Disclosure [Line Items]
Income from continuing operations less noncontrolling interests	$ 52,739		$ 63,718		$ 112,000		$ 132,476
Income from discontinued operations, net of tax			3,610		3,497		5,272
Net income attributable to McDermott International, Inc.	$ 52,739		$ 67,328		$ 115,497		$ 137,748
Weighted average common shares (basic)	235,681,213		234,573,031		235,444,733		234,207,053
Effect of dilutive securities:
Stock options, restricted stock and restricted stock units	1,779,552	[1]	2,971,643	[1]	1,951,964	[1]	2,938,073	[1]
Adjusted weighted average common shares and assumed exercises of stock options and vesting of stock awards (diluted)	237,460,765		237,544,674		237,396,697		237,145,126
Basic earnings per share:
Income from continuing operations less noncontrolling interests	$ 0.22		$ 0.27		$ 0.48		$ 0.57
Income from discontinued operations, net of tax			$ 0.02		$ 0.01		$ 0.02
Net income attributable to McDermott International, Inc.	$ 0.22		$ 0.29		$ 0.49		$ 0.59
Diluted earnings per share:
Income from continuing operations less noncontrolling interests	$ 0.22		$ 0.27		$ 0.47		$ 0.56
Income from discontinued operations, net of tax			$ 0.02		$ 0.01		$ 0.02
Net income attributable to McDermott International, Inc.	$ 0.22		$ 0.28		$ 0.49		$ 0.58

[1] Approximately 1.8 million and 3.6 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 and six-month periods ended June 30, 2012, respectively. Approximately 0.4 million shares underlying outstanding stock-based awards were excluded from the computation of diluted earnings per share for each of the three-month and six-month periods ended June 30, 2011.