Disclosures about fair value of assets and liabilities (Details 4) (Fair Value, Measurements, Nonrecurring [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Other assets measured at fair value on a nonrecurring basis
Impaired loans	$ 8,652	$ 5,822
Mortgage servicing rights	5,145	4,193
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Other assets measured at fair value on a nonrecurring basis
Impaired loans
Mortgage servicing rights
Significant Other Observable Inputs (Level 2) [Member]
Other assets measured at fair value on a nonrecurring basis
Impaired loans
Mortgage servicing rights
Significant Unobservable Inputs (Level 3) [Member]
Other assets measured at fair value on a nonrecurring basis
Impaired loans	8,652	5,822
Mortgage servicing rights	$ 5,145	$ 4,193