Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value Measurements
Transfers into or out of Levels 1-3	$ 0	$ 0
Assets:
Available for sale debt securities, fair value	220,655	200,246
Mortgage servicing rights, fair value	2,873	2,549
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Assets, Total	41,814	66,097
Other Observable Inputs (Level 2)
Assets:
Assets, Total	224,507	202,630
Significant Unobservable Inputs (Level 3)
Assets:
Mortgage servicing rights, fair value	2,873	2,549
Assets, Total	835,805	837,373
Recurring
Assets:
Assets, Total	223,528	202,795
Recurring | U.S. Treasury
Assets:
Available for sale debt securities, fair value	1,009	2,030
Recurring | Government sponsored enterprises
Assets:
Available for sale debt securities, fair value	65,453	55,180
Recurring | Asset-backed securities
Assets:
Available for sale debt securities, fair value	119,443	107,872
Recurring | Obligations of states and political subdivisions
Assets:
Available for sale debt securities, fair value	34,750	35,164
Recurring | Mortgage servicing rights
Assets:
Mortgage servicing rights, fair value	2,873	2,549
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Assets, Total	1,009	2,030
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury
Assets:
Available for sale debt securities, fair value	1,009	2,030
Recurring | Other Observable Inputs (Level 2)
Assets:
Assets, Total	219,646	198,216
Recurring | Other Observable Inputs (Level 2) | Government sponsored enterprises
Assets:
Available for sale debt securities, fair value	65,453	55,180
Recurring | Other Observable Inputs (Level 2) | Asset-backed securities
Assets:
Available for sale debt securities, fair value	119,443	107,872
Recurring | Other Observable Inputs (Level 2) | Obligations of states and political subdivisions
Assets:
Available for sale debt securities, fair value	34,750	35,164
Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Assets, Total	2,873	2,549
Recurring | Significant Unobservable Inputs (Level 3) | Mortgage servicing rights
Assets:
Mortgage servicing rights, fair value	$ 2,873	$ 2,549