Fair Value Measurements - Assets Measured at Estimated Fair Value on Nonrecurring Basis by Fair Value Hierarchy (Detail) (Fair Value, Measurements, Nonrecurring [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
ASSETS
Impaired loans	$ 14,940	$ 12,916
Other Assets, Fair Value Disclosure	1,294	117
Mortgage servicing rights	2,865	2,934
Total Assets	19,099	15,967
Level 3 [Member]
ASSETS
Impaired loans	14,940	12,916
Other Assets, Fair Value Disclosure	1,294	117
Mortgage servicing rights	2,865	2,934
Total Assets	$ 19,099	$ 15,967