Schedule of Calculation of Numerator and Denominator in Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	$ 181,092	$ 32,042
Loss from discontinued operations, net of taxes		(362)
Net income	181,092	31,680
Weighted average shares and assumed conversions	101,835	100,086
Income from continuing operations	$ 1.81	$ 0.32
Loss from discontinued operations, net of taxes
Net income	$ 1.81	$ 0.32
Income from continuing operations	$ 1.78	$ 0.32
Loss from discontinued operations, net of taxes
Net income	$ 1.78	$ 0.32
Earnings Per Share, Basic
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	181,092	32,042
Loss from discontinued operations, net of taxes		(362)
Net income	181,092	31,680
Weighted average common shares outstanding, basic	100,070	99,292
Earnings Per Share, Diluted
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	181,092	32,042
Loss from discontinued operations, net of taxes		(362)
Net income	$ 181,092	$ 31,680
Weighted average common shares outstanding, diluted	100,070	99,292
Stock options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	1,556	631
Restricted stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	209	163