Goodwill, Core Deposit Intangible and Other Intangible Assets - Summary of Changes in Goodwill, Core Deposit Intangible Assets and Customer Relationship Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Schedule Of Goodwill And Intangible Assets [Line Items]
Beginning balance, Goodwill	$ 148,353	$ 145,638	$ 148,353	$ 128,177
Additions				17,461
Ending balance, Goodwill	148,353	145,638	148,353	145,638
Amortization	(1,947)	(2,003)	(5,732)	(5,735)
Core Deposits
Schedule Of Goodwill And Intangible Assets [Line Items]
Beginning balance	25,459	32,982	29,111	30,360
Additions				6,220
Amortization	(1,825)	(1,936)	(5,477)	(5,534)
Ending balance	23,634	31,046	23,634	31,046
Accumulated amortization	$ 31,832	$ 24,420	$ 31,832	$ 24,420
Weighted average remaining amortization period	5 years 9 months 18 days	6 years 8 months 12 days	5 years 9 months 18 days	6 years 8 months 12 days
Customer Relationships
Schedule Of Goodwill And Intangible Assets [Line Items]
Beginning balance	$ 2,658	$ 2,926	$ 2,791	$ 3,059
Amortization	(122)	(67)	(255)	(200)
Ending balance	2,536	2,859	2,536	2,859
Accumulated amortization	$ 680	$ 358	$ 680	$ 358
Weighted average remaining amortization period	9 years 8 months 12 days	10 years 8 months 12 days	9 years 8 months 12 days	10 years 8 months 12 days