Income Taxes (Schedule of Income Tax Expense) (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									$ 5,107	$ 11,301	$ 11,282
State									457	463	433
Total									5,564	11,764	11,715
Deferred:
Federal									5,318	17	(602)
Income tax expense	$ 1,904	$ 2,992	$ 2,894	$ 3,092	$ 2,536	$ 3,054	$ 3,257	$ 2,934	$ 10,882	$ 11,781	$ 11,113