Fair Value Measurements (Details 5) (Non-recurring, USD $)	3 Months Ended
	Sep. 30, 2013 Impaired loans	Sep. 30, 2013 Partnership investments	Sep. 30, 2013 Mortgage servicing rights	Sep. 30, 2013 Repossessions	Sep. 30, 2013 Other real estate	Sep. 30, 2013 Level 3	Dec. 31, 2012 Level 3	Sep. 30, 2013 Level 3 Partnership investments	Dec. 31, 2012 Level 3 Partnership investments	Sep. 30, 2013 Level 3 Mortgage servicing rights	Dec. 31, 2012 Level 3 Mortgage servicing rights	Sep. 30, 2013 Level 3 Repossessions	Dec. 31, 2012 Level 3 Repossessions	Sep. 30, 2013 Level 3 Other real estate	Dec. 31, 2012 Level 3 Other real estate	Sep. 30, 2013 Total	Dec. 31, 2012 Total	Sep. 30, 2013 Total Partnership investments	Dec. 31, 2012 Total Partnership investments	Sep. 30, 2013 Total Mortgage servicing rights	Dec. 31, 2012 Total Mortgage servicing rights	Sep. 30, 2013 Total Repossessions	Dec. 31, 2012 Total Repossessions	Sep. 30, 2013 Total Other real estate	Dec. 31, 2012 Total Other real estate
Fair value measurements
Impairment charges (recoveries)	$ 0	$ (70,000)	$ 0	$ 0	$ 100,000
Impaired loans - collateral based						7,608,000	2,027,000									7,608,000	2,027,000
Accrued income and other assets								2,017,000	2,032,000	4,878,000	4,645,000	2,811,000	63,000	5,953,000	5,344,000			2,017,000	2,032,000	4,878,000	4,645,000	2,811,000	63,000	5,953,000	5,344,000
Assets measured at fair value						$ 23,267,000	$ 14,111,000									$ 23,267,000	$ 14,111,000