Goodwill and Other Intangible Assets - Components of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 34,248	$ 27,980
Accumulated Amortization and Fair Value Adjustments	17,597	15,360
Net Carrying Amount	16,651	12,620
Covenants Not To Compete [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	710	0
Accumulated Amortization and Fair Value Adjustments	205	0
Net Carrying Amount	505	0
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,788	1,520
Accumulated Amortization and Fair Value Adjustments	1,004	276
Net Carrying Amount	5,784	1,244
Customer Related Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	12,381	14,227
Accumulated Amortization and Fair Value Adjustments	8,504	8,728
Net Carrying Amount	3,877	5,499
Mortgage Servicing Rights [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	14,369	12,233
Accumulated Amortization and Fair Value Adjustments	7,884	6,356
Net Carrying Amount	$ 6,485	$ 5,877