Computation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share Disclosure [Line Items]
Income from continuing operations less noncontrolling interests	$ 20,553	$ 59,261
Total income from discontinued operations, net of tax		3,497
Net income attributable to McDermott International, Inc.	$ 20,553	$ 62,758
Weighted average common shares (basic)	235,941,185	235,208,252
Effect of dilutive securities:
Stock options, restricted stock and restricted stock units(1)	3,258,696	2,124,375
Adjusted weighted average common shares and assumed exercises of stock options and vesting of stock awards (diluted)	239,199,881	237,332,627
Basic earnings per share:
Income from continuing operations less noncontrolling interests	$ 0.09	$ 0.25
Income from discontinued operations, net of tax		$ 0.01
Net income attributable to McDermott International, Inc.	$ 0.09	$ 0.27
Diluted earnings per share:
Income from continuing operations less noncontrolling interests	$ 0.09	$ 0.25
Income from discontinued operations, net of tax		$ 0.01
Net income attributable to McDermott International, Inc.	$ 0.09	$ 0.26