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:
Federal									$ 6,195	$ 5,372	$ 5,435
State									718	980	920
Deferred:
Federal									933	1,983	1,178
State									41	162	90
Total income tax expense	$ 1,607	$ 1,890	$ 2,205	$ 2,185	$ 1,683	$ 2,358	$ 2,229	$ 2,227	$ 7,887	$ 8,497	$ 7,623