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		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	$ 20,429	$ 37,334	$ 201,521	$ 69,376
Loss from discontinued operations, net of taxes				(362)
Net income	20,429	37,334	201,521	69,014
Weighted average shares and assumed conversions	108,991	100,465	105,433	100,276
Income from continuing operations	$ 0.19	$ 0.37	$ 1.94	$ 0.70
Loss from discontinued operations, net of taxes
Net income	$ 0.19	$ 0.37	$ 1.94	$ 0.70
Income from continuing operations	$ 0.19	$ 0.37	$ 1.91	$ 0.69
Loss from discontinued operations, net of taxes
Net income	$ 0.19	$ 0.37	$ 1.91	$ 0.69
Basic Earnings Per Share
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	20,429	37,334	201,521	69,376
Loss from discontinued operations, net of taxes				(362)
Net income	20,429	37,334	201,521	69,014
Weighted average common shares outstanding, basic	107,400	99,570	103,755	99,431
Diluted Earnings Per Share
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	20,429	37,334	201,521	69,376
Loss from discontinued operations, net of taxes				(362)
Net income	$ 20,429	$ 37,334	$ 201,521	$ 69,014
Weighted average common shares outstanding, diluted	107,400	99,570	103,755	99,431
Stock options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	1,284	767	1,420	699
Restricted stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	307	128	258	146