Loans and Allowance - Changes in Allowance for Loan Losses by Loan Segment (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Allowance for loan losses:
Beginning balance	$ 121,119	$ 81,274	$ 80,284	$ 80,552
Provision for losses	12,544	600	54,191	2,300
Recoveries on loans	427	596	1,417	3,035
Loans charged off	(7,364)	(1,899)	(9,166)	(5,316)
Ending balance	126,726	80,571	126,726	80,571
Commercial
Allowance for loan losses:
Beginning balance	44,678	33,202	32,902	32,657
Provision for losses	7,299	130	19,240	466
Recoveries on loans	197	149	746	1,035
Loans charged off	(6,827)	(480)	(7,541)	(1,157)
Ending balance	45,347	33,001	45,347	33,001
Commercial Real Estate
Allowance for loan losses:
Beginning balance	46,918	29,531	28,778	29,609
Provision for losses	2,990	370	21,129	1,459
Recoveries on loans	46	143	271	1,166
Loans charged off	0	(1,078)	(224)	(3,268)
Ending balance	49,954	28,966	49,954	28,966
Consumer
Allowance for loan losses:
Beginning balance	8,445	4,070	4,035	3,964
Provision for losses	971	40	5,678	181
Recoveries on loans	54	105	152	323
Loans charged off	(92)	(109)	(487)	(362)
Ending balance	9,378	4,106	9,378	4,106
Residential
Allowance for loan losses:
Beginning balance	21,078	14,471	14,569	14,322
Provision for losses	1,284	60	8,144	194
Recoveries on loans	130	199	248	511
Loans charged off	(445)	(232)	(914)	(529)
Ending balance	$ 22,047	$ 14,498	$ 22,047	$ 14,498

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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