Income Taxes - Company's Net Deferred Tax Asset Recorded in Other Assets (Detail) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Allowance for losses and reserve for unfunded commitments	$ 14,809,000	$ 16,182,000
Deferred compensation	2,743,000	2,827,000
Accrued pension liability	9,220,000	8,597,000
Accrued bonus	1,727,000	1,326,000
Other accrued expenses	781,000	143,000
Unfunded status of the supplemental retirement plans	1,982,000	2,411,000
State taxes	2,257,000	2,297,000
Share based compensation	2,063,000	2,701,000
Nonaccrual interest	408,000	1,979,000
OREO write downs	132,000	241,000
Indemnification asset	313,000	219,000
Acquisition cost basis	3,996,000	5,118,000
Unrealized loss on securities	3,730,000
Tax credits	491,000	491,000
Net operating loss carryforwards	3,354,000	5,252,000
Other	981,000	889,000
Total deferred tax assets	48,987,000	50,673,000
Deferred tax liabilities:
Securities income	(1,362,000)	(1,362,000)
Unrealized gain on securities		(902,000)
Depreciation	(3,032,000)	(2,654,000)
Merger related fixed asset valuations	(54,000)	(54,000)
Securities accretion	(478,000)	(485,000)
Mortgage servicing rights valuation	(2,710,000)	(3,118,000)
Core deposit intangible	(1,813,000)	(2,331,000)
Junior subordinated debt	(2,616,000)	(2,699,000)
Prepaid expenses and other	(723,000)	(628,000)
Total deferred tax liability	(12,788,000)	(14,233,000)
Net deferred tax asset	$ 36,199,000	$ 36,440,000