Goodwill and Intangibles - Summary of Other Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 118,373	$ 33,024
Accumulated Amortization	(22,456)	(13,008)
Net Intangible Assets	95,917	20,016
Core deposits
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	95,711	10,658
Accumulated Amortization	(13,326)	(5,285)
Net Intangible Assets	$ 82,385	$ 5,373
Amortization Period	10 years	10 years
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 17,561	$ 17,561
Accumulated Amortization	(7,416)	(5,815)
Net Intangible Assets	$ 10,145	$ 11,746
Customer relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	7 years	7 years
Customer relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	15 years	15 years
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 221	$ 221
Accumulated Amortization	(146)	(101)
Net Intangible Assets	$ 75	$ 120
Amortization Period	5 years	5 years
Loan servicing rights(1)
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 4,880	$ 2,652
Accumulated Amortization	(1,568)	(1,301)
Net Intangible Assets	3,312	$ 1,351
Impairment losses	$ 500
Loan servicing rights(1) | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	10 years	10 years
Loan servicing rights(1) | Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	25 years	30 years
Favorable lease asset(2)
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets		$ 1,932
Accumulated Amortization		(506)
Net Intangible Assets		$ 1,426
Favorable lease asset(2) | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization Period		10 months
Favorable lease asset(2) | Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization Period		18 years