Loans and Allowance - Changes in Allowance for Loan Losses by Loan Segment (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Allowance for loan losses:
Beginning balance	$ 99,454	$ 80,902	$ 80,284	$ 80,552
Provision for losses	21,895	500	41,647	1,700
Recoveries on loans	317	1,434	990	2,439
Loans charged off	(547)	(1,562)	(1,802)	(3,417)
Ending balance	121,119	81,274	121,119	81,274
Commercial
Allowance for loan losses:
Beginning balance	38,431	33,069	32,902	32,657
Provision for losses	6,240	100	11,941	336
Recoveries on loans	106	344	549	886
Loans charged off	(99)	(311)	(714)	(677)
Ending balance	44,678	33,202	44,678	33,202
Commercial Real Estate
Allowance for loan losses:
Beginning balance	37,907	29,434	28,778	29,609
Provision for losses	8,945	320	18,139	1,089
Recoveries on loans	107	778	225	1,023
Loans charged off	(41)	(1,001)	(224)	(2,190)
Ending balance	46,918	29,531	46,918	29,531
Consumer
Allowance for loan losses:
Beginning balance	5,752	4,026	4,035	3,964
Provision for losses	2,783	36	4,707	141
Recoveries on loans	56	100	98	218
Loans charged off	(146)	(92)	(395)	(253)
Ending balance	8,445	4,070	8,445	4,070
Residential
Allowance for loan losses:
Beginning balance	17,364	14,373	14,569	14,322
Provision for losses	3,927	44	6,860	134
Recoveries on loans	48	212	118	312
Loans charged off	(261)	(158)	(469)	(297)
Ending balance	$ 21,078	$ 14,471	$ 21,078	$ 14,471

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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