Income Taxes - Company's Net Deferred Tax Asset Recorded in Other Assets (Detail) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Allowance for losses and reserve for unfunded commitments	$ 16,182,000	$ 16,284,000
Deferred compensation	2,827,000	3,115,000
Accrued pension liability	8,597,000	7,925,000
Accrued bonus	1,326,000	1,149,000
Other accrued expenses	143,000	124,000
Unfunded status of the supplemental retirement plans	2,411,000	3,315,000
State taxes	2,297,000	1,713,000
Share based compensation	2,701,000	2,534,000
Nonaccrual interest	1,979,000	2,714,000
OREO write downs	241,000	198,000
Acquisition cost basis	5,118,000	6,017,000
Tax credits	491,000	490,000
Net operating loss carryforwards	5,252,000	7,128,000
Other	889,000	625,000
Total deferred tax assets	50,454,000	53,331,000
Deferred tax liabilities:
Securities income	(1,362,000)	(1,362,000)
Unrealized gain on securities	(902,000)	(1,699,000)
Depreciation	(2,654,000)	(3,072,000)
Merger related fixed asset valuations	(54,000)	(54,000)
Securities accretion	(485,000)	(287,000)
Mortgage servicing rights valuation	(3,118,000)	(2,977,000)
Indemnification asset	219,000	147,000
Core deposit intangible	(2,331,000)	(2,802,000)
Junior subordinated debt	(2,699,000)	(2,782,000)
Prepaid expenses and other	(628,000)	(737,000)
Total deferred tax liability	(14,014,000)	(15,625,000)
Net deferred tax asset	$ 36,440,000	$ 37,706,000