Earnings per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations, net of tax	$ 22,244	$ 22,122
Loss from discontinued operations, net of tax	(3)	0
Net income	$ 22,241	$ 22,122
Weighted average common shares outstanding - Basic	40,360	39,484
Dilutive effect of employee stock grants	556	656
Weighted average shares - Diluted	43,081	42,545
Basic earnings per common share from continuing operations	$ 0.55	$ 0.56
Basic loss per common share from discontinued operations	$ 0.00	$ 0.00
Basic earnings per common share	$ 0.55	$ 0.56
Diluted earnings per common share from continuing operations	$ 0.52	$ 0.52
Diluted loss per common share from discontinued operations	$ 0.00	$ 0.00
Diluted earnings per common share	$ 0.52	$ 0.52
Class B common shares [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Weighted average common shares outstanding - Basic	2,165	2,405