Earnings per Share (Details) (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
Components of basic and diluted earnings per share
Income from continuing operations	$ 21,308	$ 15,310	$ 58,404	$ 43,358
Income (loss) from discontinued operations, net of tax		60	(9,094)	466
Net income available for common stockholders	$ 21,308	$ 15,370	$ 49,310	$ 43,824
Weighted average common shares outstanding - basic	25,071	24,638	24,930	24,493
Dilutive effect of stock-based awards	976	966	990	1,143
Weighted average common shares outstanding - diluted	26,047	25,604	25,920	25,636
Basic earnings (loss) per share from:
Continuing operations	$ 0.85	$ 0.62	$ 2.34	$ 1.77
Discontinued operations	$ 0.00	$ 0.00	$ (0.36)	$ 0.02
Net basic earnings per share	$ 0.85	$ 0.62	$ 1.98	$ 1.79
Diluted earnings (loss) per share from:
Continuing operations	$ 0.82	$ 0.60	$ 2.25	$ 1.69
Discontinued operations	$ 0.00	$ 0.00	$ (0.36)	$ 0.02
Net diluted earnings per share	$ 0.82	$ 0.60	$ 1.90	$ 1.71