Loans and Leases and Allowance for Credit Losses - Recorded investment in loans by portfolio segment and the balance of the allowance for loan losses (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment	$ 2,312	$ 3,256
Allowance for Loan Losses, Collectively evaluated for impairment	61,541	57,957
Allowance for Loan Losses, PCI	760	13
Allowance for Loan Losses, Ending balance	64,613	61,226	$ 63,424	$ 70,990
Loans Outstanding, Ending Balance	8,383,401	7,735,572
Loans Receivable
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment	2,312	3,256
Allowance for Loan Losses, Collectively evaluated for impairment	58,131	55,645
Allowance for Loan Losses, PCI	760	13
Allowance for Loan Losses, Ending balance	61,203	58,914	61,422	68,448
Loans Outstanding, Individually evaluated for impairment	55,449	62,310
Loans Outstanding, Collectively evaluated for impairment	8,253,503	7,574,748
PCI Loans	74,449	98,514
Loans Outstanding, Ending Balance	8,383,401	7,735,572
Loans Receivable \| Home equity lines of credit
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment	1	0
Allowance for Loan Losses, Collectively evaluated for impairment	4,740	5,177
Allowance for Loan Losses, PCI	11	0
Allowance for Loan Losses, Ending balance	4,752	5,177	4,599	5,956
Loans Outstanding, Individually evaluated for impairment	276	101
Loans Outstanding, Collectively evaluated for impairment	692,122	728,235
PCI Loans	1,612	2,891
Loans Outstanding, Ending Balance	694,010	731,227
Loans Receivable \| Indirect auto
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment	26	0
Allowance for Loan Losses, Collectively evaluated for impairment	973	1,550
Allowance for Loan Losses, PCI	0	0
Allowance for Loan Losses, Ending balance	999	1,550	1,802	1,393
Loans Outstanding, Individually evaluated for impairment	1,237	1,396
Loans Outstanding, Collectively evaluated for impairment	206,455	356,789
PCI Loans	0	0
Loans Outstanding, Ending Balance	207,692	358,185
Loans Receivable \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
PCI Loans	62,420	80,898
Loans Outstanding, Ending Balance	6,099,443	5,362,093
Loans Receivable \| Commercial \| Owner occupied commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment	862	1,255
Allowance for Loan Losses, Collectively evaluated for impairment	11,328	13,521
Allowance for Loan Losses, PCI	17	0
Allowance for Loan Losses, Ending balance	12,207	14,776	16,446	18,016
Loans Outstanding, Individually evaluated for impairment	17,602	21,823
Loans Outstanding, Collectively evaluated for impairment	1,620,450	1,876,411
PCI Loans	9,852	25,759
Loans Outstanding, Ending Balance	1,647,904	1,923,993
Loans Receivable \| Commercial \| Income producing commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment	402	562
Allowance for Loan Losses, Collectively evaluated for impairment	10,671	8,813
Allowance for Loan Losses, PCI	0	6
Allowance for Loan Losses, Ending balance	11,073	9,381	8,843	11,548
Loans Outstanding, Individually evaluated for impairment	16,584	16,483
Loans Outstanding, Collectively evaluated for impairment	1,757,525	1,533,851
PCI Loans	38,311	44,840
Loans Outstanding, Ending Balance	1,812,420	1,595,174
Loans Receivable \| Commercial \| Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment	71	156
Allowance for Loan Losses, Collectively evaluated for impairment	9,974	10,367
Allowance for Loan Losses, PCI	292	0
Allowance for Loan Losses, Ending balance	10,337	10,523	13,405	9,553
Loans Outstanding, Individually evaluated for impairment	2,491	3,813
Loans Outstanding, Collectively evaluated for impairment	787,760	699,266
PCI Loans	5,907	8,857
Loans Outstanding, Ending Balance	796,158	711,936
Loans Receivable \| Commercial \| Equipment financing
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment	0	0
Allowance for Loan Losses, Collectively evaluated for impairment	5,045	0
Allowance for Loan Losses, PCI	407	0
Allowance for Loan Losses, Ending balance	5,452	0	0	0
Loans Outstanding, Individually evaluated for impairment	0	0
Loans Outstanding, Collectively evaluated for impairment	556,672	0
PCI Loans	7,942	0
Loans Outstanding, Ending Balance	564,614	0
Loans Receivable \| Commercial \| Commercial & industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment	32	27
Allowance for Loan Losses, Collectively evaluated for impairment	4,761	3,944
Allowance for Loan Losses, PCI	9	0
Allowance for Loan Losses, Ending balance	4,802	3,971	3,810	4,433
Loans Outstanding, Individually evaluated for impairment	1,621	2,654
Loans Outstanding, Collectively evaluated for impairment	1,276,318	1,126,894
PCI Loans	408	1,442
Loans Outstanding, Ending Balance	1,278,347	1,130,990
Loans Receivable \| Residential \| Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment	51	75
Allowance for Loan Losses, Collectively evaluated for impairment	2,382	2,654
Allowance for Loan Losses, PCI	0	0
Allowance for Loan Losses, Ending balance	2,433	2,729	3,264	4,002
Loans Outstanding, Individually evaluated for impairment	1,207	1,577
Loans Outstanding, Collectively evaluated for impairment	209,070	180,978
PCI Loans	734	464
Loans Outstanding, Ending Balance	211,011	183,019
Loans Receivable \| Residential \| Residential mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment	861	1,174
Allowance for Loan Losses, Collectively evaluated for impairment	7,410	8,919
Allowance for Loan Losses, PCI	24	4
Allowance for Loan Losses, Ending balance	8,295	10,097	8,545	12,719
Loans Outstanding, Individually evaluated for impairment	14,220	14,193
Loans Outstanding, Collectively evaluated for impairment	1,025,862	946,210
PCI Loans	9,150	13,141
Loans Outstanding, Ending Balance	1,049,232	973,544
Loans Receivable \| Consumer direct
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment	6	7
Allowance for Loan Losses, Collectively evaluated for impairment	847	700
Allowance for Loan Losses, PCI	0	3
Allowance for Loan Losses, Ending balance	853	710	708	828
Loans Outstanding, Individually evaluated for impairment	211	270
Loans Outstanding, Collectively evaluated for impairment	121,269	126,114
PCI Loans	533	1,120
Loans Outstanding, Ending Balance	122,013	127,504
Loans Receivable \| Allowance for unfunded commitments
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment	0	0
Allowance for Loan Losses, Collectively evaluated for impairment	3,410	2,312
Allowance for Loan Losses, PCI	0	0
Allowance for Loan Losses, Ending balance	$ 3,410	$ 2,312	$ 2,002	$ 2,542

Reserve for loans impairments recorded after acquisition as a result of current information and events which result in it being probable that estimated cash flows will be less than previously expected or because actual cash flows are less than cash flows previously expected. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that was acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 15
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538

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- Definition

The recorded balance, net of any applicable reductions (for example, unamortized accretable yield and allowance for loan losses). This relates to loans not accounted for debt securities with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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A valuation allowance for financing receivables that are expected to be uncollectible.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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-Publisher FASB
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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

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-Publisher FASB
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The balance of financing receivables that were collectively evaluated for impairment.

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The balance of financing receivables that were individually evaluated for impairment.

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- Definition

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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