Goodwill and Other Intangible Assets - Components of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 27,980	$ 23,956
Accumulated Amortization and Fair Value Adjustments	15,360	11,776
Net Carrying Amount	12,620	12,180
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,520	0
Accumulated Amortization and Fair Value Adjustments	276	0
Net Carrying Amount	1,244	0
Customer Related Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	14,227	13,397
Accumulated Amortization and Fair Value Adjustments	8,728	6,726
Net Carrying Amount	5,499	6,671
Mortgage Servicing Rights [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	12,233	10,559
Accumulated Amortization and Fair Value Adjustments	6,356	5,050
Net Carrying Amount	$ 5,877	$ 5,509