Income Taxes - Company's Net Deferred Tax Asset Recorded in Other Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Allowance for losses and reserve for unfunded commitments	$ 9,871	$ 10,394
Deferred compensation	2,342	2,780
Accrued pension liability	3,309	9,734
Other accrued expenses	1,678	1,175
Additional unfunded status of the supplemental retirement plans	9,868	1,420
Operating lease liability	8,142
State taxes	2,441	1,864
Share based compensation	803	1,132
Nonaccrual interest	649	814
Acquisition cost basis	4,556	6,714
Unrealized loss on securities	0	6,201
Tax credits	576	623
Tax credit related to operating losses	1,578	2,442
Other	348	423
Total deferred tax assets	46,161	45,716
Deferred tax liabilities:
Securities income	(762)	(1,020)
Depreciation	(6,109)	(5,572)
Right of use asset	(8,242)
Merger related fixed asset valuations	(30)	(26)
Securities accretion	(560)	(426)
Mortgage servicing rights valuation	(1,813)	(2,073)
Core deposit intangible	(6,453)	(8,234)
Junior subordinated debt	(1,672)	(1,729)
Prepaid expenses and other	(469)	(582)
Total deferred tax liability	(27,111)	(19,662)
Net deferred tax asset	$ 19,050	$ 26,054