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, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	$ 42,339	$ 39,347	$ 111,715	$ 122,403
Loss from discontinued operations, net of taxes		(107)	(362)	(415)
Net income	42,339	39,240	111,353	121,988
Weighted average shares and assumed conversions	100,842	105,020	100,464	107,414
Income from continuing operations	$ 0.42	$ 0.38	$ 1.12	$ 1.14
Loss from discontinued operations, net of taxes
Net income	$ 0.42	$ 0.38	$ 1.12	$ 1.14
Income from continuing operations	$ 0.42	$ 0.37	$ 1.11	$ 1.14
Loss from discontinued operations, net of taxes
Net income	$ 0.42	$ 0.37	$ 1.11	$ 1.14
Earnings Per Share, Basic
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	42,339	39,347	111,715	122,403
Loss from discontinued operations, net of taxes		(107)	(362)	(415)
Net income	42,339	39,240	111,353	121,988
Weighted average common shares outstanding, basic	99,637	104,254	99,500	106,624
Earnings Per Share, Diluted
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	42,339	39,347	111,715	122,403
Loss from discontinued operations, net of taxes		(107)	(362)	(415)
Net income	$ 42,339	$ 39,240	$ 111,353	$ 121,988
Weighted average common shares outstanding, diluted	99,637	104,254	99,500	106,624
Stock options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	973	550	790	621
Restricted stock-based compensation
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	232	216	174	169