Earnings per Share - Components of Basic and Diluted 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 And Diluted [Abstract]
Income from continuing operations	$ 11,012	$ 18,988	$ 30,460	$ 37,096
Loss from discontinued operations, net of tax		(2,392)		(9,094)
Net income available for common stockholders	$ 11,012	$ 16,596	$ 30,460	$ 28,002
Weighted average common shares outstanding - basic	23,966	24,919	23,707	24,850
Dilutive effect of stock-based awards	849	906	945	972
Dilutive effect of convertible senior notes	40
Weighted average common shares outstanding - diluted	24,855	25,825	24,652	25,822
Basic earnings (loss) per share from:
Continuing operations	$ 0.46	$ 0.76	$ 1.28	$ 1.49
Discontinued operations		$ (0.09)		$ (0.36)
Net basic earnings per share	$ 0.46	$ 0.67	$ 1.28	$ 1.13
Diluted earnings (loss) per share from:
Continuing operations	$ 0.44	$ 0.74	$ 1.24	$ 1.44
Discontinued operations		$ (0.10)		$ (0.36)
Net diluted earnings per share	$ 0.44	$ 0.64	$ 1.24	$ 1.08