Goodwill and Intangible Assets - Schedule of Acquired Intangible Assets, Other than Goodwill (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 17,047	$ 16,902
Accumulated Amortization	8,437	7,550
Net Carrying Amount	8,610	9,352
MSRs [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	2,255	2,110
Accumulated Amortization	623	446
Net Carrying Amount	1,632	1,664
Core deposit intangibles [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	14,792	14,792
Accumulated Amortization	7,814	7,104
Net Carrying Amount	$ 6,978	$ 7,688