Fair Value Measurement (Details) (Fair value measurement on a recurring basis [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Recorded amount of assets and liabilities measured at fair value on a recurring basis
Total assets measured at fair value	$ 167,579	$ 233,826
Obligations of U.S. government corporations and agencies [Member]
Recorded amount of assets and liabilities measured at fair value on a recurring basis
Total assets measured at fair value	151,701	217,384
Obligations of states and political subdivision [Member]
Recorded amount of assets and liabilities measured at fair value on a recurring basis
Total assets measured at fair value	9,421	10,028
Corporate debt securities [Member]
Recorded amount of assets and liabilities measured at fair value on a recurring basis
Total assets measured at fair value	1,905	1,811
Mortgage servicing rights [Member]
Recorded amount of assets and liabilities measured at fair value on a recurring basis
Total assets measured at fair value	4,552	4,603
Level 1 [Member]
Recorded amount of assets and liabilities measured at fair value on a recurring basis
Total assets measured at fair value
Level 1 [Member] | Obligations of U.S. government corporations and agencies [Member]
Recorded amount of assets and liabilities measured at fair value on a recurring basis
Total assets measured at fair value
Level 1 [Member] | Obligations of states and political subdivision [Member]
Recorded amount of assets and liabilities measured at fair value on a recurring basis
Total assets measured at fair value
Level 1 [Member] | Corporate debt securities [Member]
Recorded amount of assets and liabilities measured at fair value on a recurring basis
Total assets measured at fair value
Level 1 [Member] | Mortgage servicing rights [Member]
Recorded amount of assets and liabilities measured at fair value on a recurring basis
Total assets measured at fair value
Level 2 [Member]
Recorded amount of assets and liabilities measured at fair value on a recurring basis
Total assets measured at fair value	163,027	229,223
Level 2 [Member] | Obligations of U.S. government corporations and agencies [Member]
Recorded amount of assets and liabilities measured at fair value on a recurring basis
Total assets measured at fair value	151,701	217,384
Level 2 [Member] | Obligations of states and political subdivision [Member]
Recorded amount of assets and liabilities measured at fair value on a recurring basis
Total assets measured at fair value	9,421	10,028
Level 2 [Member] | Corporate debt securities [Member]
Recorded amount of assets and liabilities measured at fair value on a recurring basis
Total assets measured at fair value	1,905	1,811
Level 3 [Member]
Recorded amount of assets and liabilities measured at fair value on a recurring basis
Total assets measured at fair value	4,552	4,603
Level 3 [Member] | Mortgage servicing rights [Member]
Recorded amount of assets and liabilities measured at fair value on a recurring basis
Total assets measured at fair value	$ 4,552	$ 4,603