Loans and Allowance - Changes in Allowance for Loan Losses by Loan Segment (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Allowance for loan losses:
Beginning balance	$ 66,037	$ 62,453
Provision for losses	2,385	550
Recoveries on loans	1,268	1,634
Loans charged-off	(1,465)	(2,551)
Ending balance	68,225	62,086
Commercial
Allowance for loan losses:
Beginning balance	27,696	26,478
Provision for losses	1,197	139
Recoveries on loans	366	292
Loans charged-off	(735)	(645)
Ending balance	28,524	26,264
Commercial Real Estate
Allowance for loan losses:
Beginning balance	23,661	22,145
Provision for losses	247	214
Recoveries on loans	564	952
Loans charged-off	(152)	(994)
Ending balance	24,320	22,317
Consumer
Allowance for loan losses:
Beginning balance	2,923	2,689
Provision for losses	249	33
Recoveries on loans	101	78
Loans charged-off	(153)	(153)
Ending balance	3,120	2,647
Residential
Allowance for loan losses:
Beginning balance	11,755	11,139
Provision for losses	692	164
Recoveries on loans	237	312
Loans charged-off	(425)	(759)
Ending balance	12,259	10,856
Finance Leases
Allowance for loan losses:
Beginning balance	2	2
Provision for losses
Recoveries on loans
Loans charged-off
Ending balance	$ 2	$ 2

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

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 6.L.1)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

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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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