Loans, Allowance for Loan Losses and Credit Quality (Allowance Allocations) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	$ 5,520,205	$ 5,475,716
Ending Balance: Individually Evaluated for Impairment	48,819	51,410
Financing Receivable, Net	4,008,383	3,966,324
Ending Balance: Total Loans by Group	5,589,231	5,547,721
Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net	20,207	20,595
Commercial and Industrial [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	830,477	838,129
Ending Balance: Individually Evaluated for Impairment	4,859	5,147
Financing Receivable, Net	835,336	843,276
Ending Balance: Total Loans by Group	835,336	843,276
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, Net	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	2,678,161	2,619,294
Ending Balance: Individually Evaluated for Impairment	22,808	22,986
Financing Receivable, Net	2,711,857	2,653,434
Ending Balance: Total Loans by Group	2,711,857	2,653,434
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, Net	10,888	11,154
Construction Loans [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	357,867	373,064
Ending Balance: Individually Evaluated for Impairment	0	304
Financing Receivable, Net	357,867	373,368
Ending Balance: Total Loans by Group	357,867	373,368
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, Net	0	0
Small Business [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	102,384	95,225
Ending Balance: Individually Evaluated for Impairment	939	1,021
Financing Receivable, Net	103,323	96,246
Ending Balance: Total Loans by Group	103,323	96,246
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, Net	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	609,153	614,014
Ending Balance: Individually Evaluated for Impairment	13,673	15,405
Ending Balance: Total Loans by Group	631,888	638,606
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, Net	9,062	9,187
Consumer Home Equity [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	929,050	921,563
Ending Balance: Individually Evaluated for Impairment	6,006	5,989
Ending Balance: Total Loans by Group	935,311	927,803
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, Net	255	251
Consumer Other [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment	13,113	14,427
Ending Balance: Individually Evaluated for Impairment	534	558
Ending Balance: Total Loans by Group	13,649	14,988
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, Net	$ 2	$ 3

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

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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
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524

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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
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522

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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
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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