Intangible Assets - Amortization Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Core deposit premiums	$ 786	$ 931	$ 1,076
Customer relationship and other intangibles	1,869	1,073	1,474
Mortgage servicing rights	85	123	120
Total amortization expense of intangible assets	$ 2,740	$ 2,127	$ 2,670