Intangible Assets and Goodwill - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 39,247	$ 32,003
Accumulated Amortization	(16,639)	(15,533)
Net Carrying Amount	22,608	16,470
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	35,856	25,907
Accumulated Amortization	(14,131)	(11,113)
Net Carrying Amount	21,725	14,794
Customer Relationship Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3,391	5,699
Accumulated Amortization	(2,508)	(4,115)
Net Carrying Amount	$ 883	1,584
Mortgage Servicing Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount		397
Accumulated Amortization		(305)
Net Carrying Amount		$ 92