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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Schedule Of Goodwill And Intangible Assets [Line Items]
Beginning balance, Goodwill	$ 145,638	$ 127,536	$ 128,177	$ 54,562
Additions			17,461	72,974
Ending balance, Goodwill	145,638	127,536	145,638	127,536
Amortization	(2,003)	(1,898)	(5,735)	(3,795)
Core Deposits
Schedule Of Goodwill And Intangible Assets [Line Items]
Beginning balance	32,982	33,917	30,360	16,720
Additions			6,220	19,060
Amortization	(1,936)	(1,822)	(5,534)	(3,685)
Ending balance	31,046	32,095	31,046	32,095
Accumulated amortization	$ 24,420	$ 17,151	$ 24,420	$ 17,151
Weighted average remaining amortization period	6 years 8 months 12 days	7 years 1 month 6 days	6 years 8 months 12 days	7 years 1 month 6 days
Customer Relationships
Schedule Of Goodwill And Intangible Assets [Line Items]
Beginning balance	$ 2,926	$ 3,194	$ 3,059
Additions				$ 3,216
Amortization	(67)	(67)	(200)	(89)
Ending balance	2,859	3,127	2,859	3,127
Accumulated amortization	$ 358	$ 89	$ 358	$ 89
Weighted average remaining amortization period	10 years 8 months 12 days	11 years 8 months 12 days	10 years 8 months 12 days	11 years 8 months 12 days