Income Taxes (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Provision for income taxes attributable to income from continuing operations
Tax at statutory rate (35%)									$ 17,641	$ 16,438	$ 15,810
State taxes (net of federal benefit)									1,637	2,044	1,875
Business meals and entertainment - non-deductible									717	659	627
Reserves for uncertain tax positions									(432)	(844)	(1,284)
Other, net									(235)	86	(11)
Total income tax expense from continuing operations	$ (58)	$ 2,458	$ 3,512	$ 13,416	$ (1,913)	$ 1,614	$ 5,095	$ 13,587	$ 19,328	$ 18,383	$ 17,017
Effective income tax rate									38.30%	39.10%	37.70%