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, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	$ 37,334	$ 42,616	$ 69,376	$ 83,056
Loss from discontinued operations, net of taxes		(198)	(362)	(308)
Net income	37,334	42,418	69,014	82,748
Weighted average shares and assumed conversions	100,465	107,728	100,276	108,631
Income from continuing operations	$ 0.37	$ 0.40	$ 0.70	$ 0.77
Loss from discontinued operations, net of taxes
Net income	$ 0.37	$ 0.40	$ 0.70	$ 0.77
Income from continuing operations	$ 0.37	$ 0.39	$ 0.69	$ 0.76
Loss from discontinued operations, net of taxes
Net income	$ 0.37	$ 0.39	$ 0.69	$ 0.76
Earnings Per Share, Basic
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	37,334	42,616	69,376	83,056
Loss from discontinued operations, net of taxes		(198)	(362)	(308)
Net income	37,334	42,418	69,014	82,748
Weighted average common shares outstanding, basic	99,570	106,977	99,431	107,828
Earnings Per Share, Diluted
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	37,334	42,616	69,376	83,056
Loss from discontinued operations, net of taxes		(198)	(362)	(308)
Net income	$ 37,334	$ 42,418	$ 69,014	$ 82,748
Weighted average common shares outstanding, diluted	99,570	106,977	99,431	107,828
Stock Options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	767	622	699	657
Restricted Stock-Based Compensation
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	128	129	146	146