Loans and Allowance - Changes in Allowance for Loan Losses by Loan Segment (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Allowance for loan losses:
Beginning balance	$ 68,225	$ 62,086	$ 66,037	$ 62,453
Provision for losses	2,875	790	5,260	1,340
Recoveries on loans	726	1,339	1,994	2,973
Loans charged-off	(1,355)	(2,029)	(2,820)	(4,580)
Ending balance	70,471	62,186	70,471	62,186
Commercial
Allowance for loan losses:
Beginning balance	28,524	26,264	27,696	26,478
Provision for losses	161	400	1,358	539
Recoveries on loans	297	683	663	975
Loans charged-off	(76)	(1,026)	(811)	(1,671)
Ending balance	28,906	26,321	28,906	26,321
Commercial Real Estate
Allowance for loan losses:
Beginning balance	24,320	22,317	23,661	22,145
Provision for losses	1,402	200	1,649	414
Recoveries on loans	175	276	739	1,228
Loans charged-off	(661)	(513)	(813)	(1,507)
Ending balance	25,236	22,280	25,236	22,280
Consumer
Allowance for loan losses:
Beginning balance	3,120	2,647	2,923	2,689
Provision for losses	286	44	535	77
Recoveries on loans	101	107	202	185
Loans charged-off	(135)	(114)	(288)	(267)
Ending balance	3,372	2,684	3,372	2,684
Residential
Allowance for loan losses:
Beginning balance	12,259	10,856	11,755	11,139
Provision for losses	1,026	146	1,718	310
Recoveries on loans	153	273	390	585
Loans charged-off	(483)	(376)	(908)	(1,135)
Ending balance	12,955	10,899	12,955	10,899
Finance Leases
Allowance for loan losses:
Beginning balance	2	2	2	2
Provision for losses
Recoveries on loans
Loans charged-off
Ending balance	$ 2	$ 2	$ 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=84173941&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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-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
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-Section S99
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-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
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-URI http://asc.fasb.org/extlink&oid=82894903&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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