Assets Measured at Fair Value on Non-Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair Value, Measurements, Nonrecurring
Assets:
Collateral-dependent impaired loans	$ 9,525	$ 18,183
Goodwill		276
Other real estate owned	1,697	1,682
Mortgage servicing rights	976	1,138
Observable Market Data (Level 2)
Assets:
Mortgage servicing rights	976
Observable Market Data (Level 2) | Fair Value, Measurements, Nonrecurring
Assets:
Mortgage servicing rights	976	1,138
Company Determined Fair Value (Level 3) | Fair Value, Measurements, Nonrecurring
Assets:
Collateral-dependent impaired loans	9,525	18,183
Goodwill		276
Other real estate owned	$ 1,697	$ 1,682