Income Taxes (Details) (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
Current tax expense
Federal									$ 9,895	$ 9,645	$ 5,509
State									3,425	3,238	1,824
Current tax expense, Total									13,320	12,883	7,333
Deferred tax benefit
Federal									(235)	(1,298)	(3,586)
State									(148)	(393)	(1,281)
Deferred tax benefit, Total									(384)	(1,691)	(4,867)
Total tax expense	$ 3,410	$ 3,616	$ 3,452	$ 2,459	$ 3,715	$ 4,318	$ 1,577	$ 1,582	$ 12,937	$ 11,192	$ 2,466