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	Dec. 31, 2014	Dec. 31, 2013
ASSETS
Loans held for sale	$ 0	$ 1,516
Impaired loans	12,916	19,197
Other real estate owned	117	317
Mortgage servicing rights	2,934	1,025
Total Assets	15,967	22,055
Level 1 [Member]
ASSETS
Loans held for sale	0	0
Impaired loans	0	0
Other real estate owned	0	0
Mortgage servicing rights	0	0
Level 2 [Member]
ASSETS
Loans held for sale	0	0
Impaired loans	0	0
Other real estate owned	0	0
Mortgage servicing rights	0	0
Level 3 [Member]
ASSETS
Loans held for sale	0	1,516
Impaired loans	12,916	19,197
Other real estate owned	117	317
Mortgage servicing rights	2,934	1,025
Total Assets	$ 15,967	$ 22,055