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Allowance for Loan Losses and Credit Quality of Loans, Credit Quality by Loan Class (Details) - USD ($) $ in Thousands | Mar. 31, 2016 | Dec. 31, 2015
--- | --- | ---
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | $ 5,967,809 | $ 5,883,133
Commercial Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 2,617,111 | 2,589,707
Consumer Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 2,138,877 | 2,096,646
Residential Mortgage Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1,211,821 | 1,196,780
Originated Loans [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 5,376,887 | 5,271,619
Originated Loans [Member] | Commercial Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 2,337,481 | 2,303,978
Originated Loans [Member] | Commercial Credit Exposure [Member] | Total Commercial and Agricultural [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1,937,559 | 1,903,057
Originated Loans [Member] | Commercial Credit Exposure [Member] | Total Commercial and Agricultural [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1,838,212 | 1,810,122
Originated Loans [Member] | Commercial Credit Exposure [Member] | Total Commercial and Agricultural [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 33,980 | 32,053
Originated Loans [Member] | Commercial Credit Exposure [Member] | Total Commercial and Agricultural [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 65,359 | 60,874
Originated Loans [Member] | Commercial Credit Exposure [Member] | Total Commercial and Agricultural [Member] | Doubtful [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 8 | 8
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 656,511 | 644,318
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 614,475 | 604,405
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 14,130 | 9,726
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 27,906 | 30,187
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Doubtful [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 0 | 0
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1,216,746 | 1,194,897
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1,161,375 | 1,144,832
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 19,483 | 21,587
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 35,888 | 28,478
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Doubtful [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 0 | 0
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 34,383 | 34,624
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 33,744 | 33,565
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1 | 311
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 630 | 740
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] | Doubtful [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 8 | 8
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural Real Estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 29,919 | 29,218
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural Real Estate [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 28,618 | 27,320
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural Real Estate [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 366 | 429
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural Real Estate [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 935 | 1,469
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural Real Estate [Member] | Doubtful [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 0 | 0
Originated Loans [Member] | Commercial Credit Exposure [Member] | Business Banking [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 399,922 | 400,921
Originated Loans [Member] | Business Banking Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 399,922 | 400,921
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Non-classified [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 386,194 | 386,397
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Classified [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 13,728 | 14,524
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 399,922 | 400,921
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] | Non-classified [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 386,194 | 386,397
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] | Classified [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 13,728 | 14,524
Originated Loans [Member] | Consumer Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 2,052,568 | 2,001,219
Originated Loans [Member] | Consumer Credit Exposure [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 2,045,193 | 1,991,910
Originated Loans [Member] | Consumer Credit Exposure [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 7,375 | 9,309
Originated Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1,536,349 | 1,477,250
Originated Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1,533,133 | 1,473,193
Originated Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 3,216 | 4,057
Originated Loans [Member] | Consumer Credit Exposure [Member] | Home Equity [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 457,280 | 464,715
Originated Loans [Member] | Consumer Credit Exposure [Member] | Home Equity [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 453,296 | 459,540
Originated Loans [Member] | Consumer Credit Exposure [Member] | Home Equity [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 3,984 | 5,175
Originated Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 58,939 | 59,254
Originated Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 58,764 | 59,177
Originated Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 175 | 77
Originated Loans [Member] | Residential Mortgage Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 986,838 | 966,422
Originated Loans [Member] | Residential Mortgage Credit Exposure [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 979,685 | 958,013
Originated Loans [Member] | Residential Mortgage Credit Exposure [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 7,153 | 8,409
Acquired Loans [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 590,922 | 611,514
Acquired Loans [Member] | Commercial Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 279,630 | 285,729
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Total Commercial and Agricultural [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 233,857 | 235,934
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Total Commercial and Agricultural [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 217,711 | 222,112
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Total Commercial and Agricultural [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 4,679 | 2,976
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Total Commercial and Agricultural [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 11,467 | 10,846
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 65,412 | 68,991
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 61,898 | 67,241
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1,824 | 802
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 1,690 | 948
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 168,445 | 166,943
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 155,813 | 154,871
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 2,855 | 2,174
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 9,777 | 9,898
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Business Banking [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 45,773 | 49,795
Acquired Loans [Member] | Business Banking Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 45,773 | 49,795
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Non-classified [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 42,271 | 46,032
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Classified [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 3,502 | 3,763
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 45,773 | 49,795
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] | Non-classified [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 42,271 | 46,032
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] | Classified [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 3,502 | 3,763
Acquired Loans [Member] | Consumer Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 86,309 | 95,427
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 85,814 | 94,822
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 495 | 605
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 21,847 | 27,775
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 21,767 | 27,670
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 80 | 105
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Home Equity [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 60,928 | 63,727
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Home Equity [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 60,578 | 63,270
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Home Equity [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 350 | 457
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 3,534 | 3,925
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 3,469 | 3,882
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 65 | 43
Acquired Loans [Member] | Residential Mortgage Credit Exposure [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 224,983 | 230,358
Acquired Loans [Member] | Residential Mortgage Credit Exposure [Member] | Performing [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | 222,329 | 227,448
Acquired Loans [Member] | Residential Mortgage Credit Exposure [Member] | Nonperforming [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Financing Receivable | $ 2,654 | $ 2,910

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