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		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	$ 52,506	$ 42,240	$ 257,121	$ 111,708
(Loss) income from discontinued operations, net of taxes	(663)	99	(3,757)	(355)
Net income	51,843	42,339	253,364	111,353
Weighted average shares and assumed conversions	116,872	100,842	109,300	100,464
Income from continuing operations	$ 0.46	$ 0.42	$ 2.38	$ 1.12
(Loss) income from discontinued operations, net of taxes	$ (0.01)		$ (0.03)
Net income	$ 0.45	$ 0.42	$ 2.35	$ 1.12
Income from continuing operations	$ 0.45	$ 0.42	$ 2.35	$ 1.11
(Loss) income from discontinued operations, net of taxes	$ (0.01)		$ (0.03)
Net income	$ 0.44	$ 0.42	$ 2.32	$ 1.11
Basic Earnings Per Share
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	52,506	42,240	257,121	111,708
(Loss) income from discontinued operations, net of taxes	(663)	99	(3,757)	(355)
Net income	51,843	42,339	253,364	111,353
Weighted average common shares outstanding, basic	115,282	99,637	107,640	99,500
Diluted Earnings Per Share
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	52,506	42,240	257,121	111,708
(Loss) income from discontinued operations, net of taxes	(663)	99	(3,757)	(355)
Net income	$ 51,843	$ 42,339	$ 253,364	$ 111,353
Weighted average common shares outstanding, diluted	115,282	99,637	107,640	99,500
Stock options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	1,165	973	1,335	790
Restricted stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	425	232	325	174