Goodwill and Other Intangible Assets - Schedule of Change in Loan Servicing Rights (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Balance at beginning of year	$ 22,084	$ 20,368	$ 16,681
Origination of loan servicing rights	8,216	7,039	8,479
Amortization expense	(6,107)	(5,323)	(4,792)
Balance at end of year	24,193	22,084	20,368
Balance at beginning of year	(471)	(900)	(289)
Impairment adjustment	388	429	(611)
Balance at end of year	(83)	(471)	(900)
Balance at end of year, net of valuation allowance	$ 24,110	$ 21,613	$ 19,468