Loans and Allowance - Changes in Allowance for Loan Losses by Loan Segment (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Allowance for loan losses:
Beginning balance	$ 80,552	$ 75,032
Provision for losses	1,200	2,500
Recoveries on loans	1,005	701
Loans charged off	(1,855)	(1,813)
Ending balance	80,902	76,420
Commercial
Allowance for loan losses:
Beginning balance	32,657	30,420
Provision for losses	236	840
Recoveries on loans	542	119
Loans charged off	(366)	(609)
Ending balance	33,069	30,770
Commercial Real Estate
Allowance for loan losses:
Beginning balance	29,609	27,343
Provision for losses	769	84
Recoveries on loans	245	339
Loans charged off	(1,189)	(61)
Ending balance	29,434	27,705
Consumer
Allowance for loan losses:
Beginning balance	3,964	3,732
Provision for losses	105	274
Recoveries on loans	118	89
Loans charged off	(161)	(199)
Ending balance	4,026	3,896
Residential
Allowance for loan losses:
Beginning balance	14,322	13,537
Provision for losses	90	1,302
Recoveries on loans	100	154
Loans charged off	(139)	(944)
Ending balance	$ 14,373	$ 14,049

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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