Fair Value Measurements (Details 2) (USD $) In Thousands, unless otherwise specified									6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Jun. 30, 2013 Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member]	Jun. 30, 2013 Fair Value, Inputs, Level 3 [Member] Impaired Loans [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Impaired Loans [Member]	Jun. 30, 2013 Fair Value, Inputs, Level 3 [Member] Other Real Estate Owned [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Other Real Estate Owned [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Mortgage Service Rights [Member]
Impaired loans with specific valuation allowances	$ 17,574		$ 27,257				$ 17,574	$ 34,383	$ 17,574	$ 34,383
Other real estate owned	2,606	5,684	6,552	12,251	18,086	21,270	2,606	6,552			2,606	6,552
MSRs	$ 1,786	$ 1,546	$ 1,308	$ 774	$ 300	$ 0	$ 1,786	$ 1,308					$ 1,308
Valuation Techniques									Market approach	Market approach	Market approach	Market approach	Market approach
Unobservable Input									Appraised value less selling costs of 5% to 10% Additional discounts of 5% to 50% to appraised value to reflect liquidation value	Appraised value less selling costs of 5% to 10% Additional discounts of 5% to 50% to appraised value to reflect liquidation value	Appraised value less selling costs of 5% to 10%	Appraised value less selling costs of 5% to 10%	Weighted average prepayment speed of 10.5%