Loans, Allowance for Loan Losses, and Credit Quality Loans Modified in a Troubled Debt Restructuring (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Modifications [Line Items]
Number of Loans	309	278	413
Recorded Investment	$ 38,870	$ 64,052	$ 59,599
Unpaid Principal Balance	40,660	71,319	68,950
Commercial and Industrial Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	15	48	85
Recorded Investment	7,681	11,833	12,827
Unpaid Principal Balance	7,711	14,543	15,834
Commercial Real Estate Owner Occupied Portfolio [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	4	12	27
Recorded Investment	1,465	8,823	11,978
Unpaid Principal Balance	1,625	9,035	12,766
Commercial Real Estate Investor Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	6	25	25
Recorded Investment	6,097	26,480	12,379
Unpaid Principal Balance	6,521	28,516	13,569
Commercial Real Estate Construction Financing Receivable [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	2	9	31
Recorded Investment	15	1,822	2,955
Unpaid Principal Balance	15	1,961	3,549
Home Equity Portfolio Segments [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	132	88	111
Recorded Investment	5,267	4,642	4,870
Unpaid Principal Balance	5,687	4,958	6,143
Installment and Credit Cards [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	2	3	13
Recorded Investment	24	193	298
Unpaid Principal Balance	26	200	302
Residential Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	148	93	121
Recorded Investment	18,321	10,259	14,292
Unpaid Principal Balance	$ 19,075	$ 12,106	$ 16,787

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Number of financing receivables that have been modified by troubled debt restructurings.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 33

-URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953676-111524

+ Details

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Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

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- Definition

Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

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