Loans, Allowance for Loan Losses and Credit Quality (Allowance Allocations) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortization of Deferred Loan Origination Fees, Net	$ 4,000	$ 2,800
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	5,418,967	4,890,383
Ending Balance: Individually Evaluated for Impairment	58,014	58,035
Financing receivable	3,922,346	3,559,403
Ending Balance: Total Loans by Group	5,498,121	4,970,733
Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing receivable	21,140	22,315
Commercial and Industrial [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	856,916	856,185
Ending Balance: Individually Evaluated for Impairment	5,596	4,654
Financing receivable	862,512	860,839
Ending Balance: Total Loans by Group	862,512	860,839
Commercial and Industrial [Member] \| Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing receivable	0	0
Commercial Real Estate [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	2,618,612	2,304,099
Ending Balance: Individually Evaluated for Impairment	29,506	30,729
Financing receivable	2,659,342	2,347,323
Ending Balance: Total Loans by Group	2,659,342	2,347,323
Commercial Real Estate [Member] \| Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing receivable	11,224	12,495
Construction Loans [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	307,908	265,501
Ending Balance: Individually Evaluated for Impairment	306	311
Financing receivable	308,214	265,994
Ending Balance: Total Loans by Group	308,214	265,994
Construction Loans [Member] \| Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing receivable	0	182
Small Business [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	91,307	84,159
Ending Balance: Individually Evaluated for Impairment	971	1,088
Financing receivable	92,278	85,247
Ending Balance: Total Loans by Group	92,278	85,247
Small Business [Member] \| Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing receivable	0	0
Residential Real Estate [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	627,031	505,799
Ending Balance: Individually Evaluated for Impairment	15,247	15,055
Ending Balance: Total Loans by Group	651,937	530,259
Residential Real Estate [Member] \| Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing receivable	9,659	9,405
Consumer Home Equity [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	901,863	858,305
Ending Balance: Individually Evaluated for Impairment	5,777	5,330
Ending Balance: Total Loans by Group	907,894	863,863
Consumer Home Equity [Member] \| Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing receivable	254	228
Consumer Other [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	15,330	16,335
Ending Balance: Individually Evaluated for Impairment	611	868
Ending Balance: Total Loans by Group	15,944	17,208
Consumer Other [Member] \| Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing receivable	$ 3	$ 5

Allowance for loans based on collective and individual evaluation of impairment by loan category.

No definition available.

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- Definition

The net increase(decrease) in interest income during the period representing the allocation of deferred loan origination fees less deferred loan origination costs using the effective interest method over the term of the debt arrangement to which they pertain taking into account the effect of prepayments.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

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-Section S99

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Direct Loan Origination Costs

-URI http://asc.fasb.org/extlink&oid=6510860

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

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

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

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-Paragraph 11B

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

+ References

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- Definition

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

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section 45

-Paragraph 2

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- Definition

Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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-Section S99

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-Subparagraph (SX 210.5-02.3)

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