Allowance for Loan Losses and Credit Quality of Loans, Credit Quality by Loan Class (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Net Loans	$ 6,198,057	$ 5,883,133
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	1,242,701	1,159,089
Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	507,784	528,442
Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	2,786,002	2,589,707
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	2,149,441	2,096,646
Residential Real Estate Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	1,262,614	1,196,780
Originated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	5,697,963	5,271,619
Originated Loans [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	2,548,384	2,303,978
Originated Loans [Member] | Commercial Loans [Member] | Total Commercial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	2,075,697	1,903,057
Originated Loans [Member] | Commercial Loans [Member] | Total Commercial and Agricultural [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	1,970,912	1,810,122
Originated Loans [Member] | Commercial Loans [Member] | Total Commercial and Agricultural [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	40,724	32,053
Originated Loans [Member] | Commercial Loans [Member] | Total Commercial and Agricultural [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	64,056	60,874
Originated Loans [Member] | Commercial Loans [Member] | Total Commercial and Agricultural [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	5	8
Originated Loans [Member] | Commercial Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	653,570	644,318
Originated Loans [Member] | Commercial Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	616,829	604,405
Originated Loans [Member] | Commercial Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	7,750	9,726
Originated Loans [Member] | Commercial Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	28,991	30,187
Originated Loans [Member] | Commercial Loans [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	0	0
Originated Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	1,351,789	1,194,897
Originated Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	1,288,409	1,144,832
Originated Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	31,053	21,587
Originated Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	32,327	28,478
Originated Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	0	0
Originated Loans [Member] | Commercial Loans [Member] | Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	37,916	34,624
Originated Loans [Member] | Commercial Loans [Member] | Agricultural [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	36,762	33,565
Originated Loans [Member] | Commercial Loans [Member] | Agricultural [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	25	311
Originated Loans [Member] | Commercial Loans [Member] | Agricultural [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	1,124	740
Originated Loans [Member] | Commercial Loans [Member] | Agricultural [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	5	8
Originated Loans [Member] | Commercial Loans [Member] | Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	32,422	29,218
Originated Loans [Member] | Commercial Loans [Member] | Agricultural Real Estate [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	28,912	27,320
Originated Loans [Member] | Commercial Loans [Member] | Agricultural Real Estate [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	1,896	429
Originated Loans [Member] | Commercial Loans [Member] | Agricultural Real Estate [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	1,614	1,469
Originated Loans [Member] | Commercial Loans [Member] | Agricultural Real Estate [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	0	0
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	472,687	400,921
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | Non-classified [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	458,864	386,397
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | Classified [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	13,823	14,524
Originated Loans [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	2,086,436	2,001,219
Originated Loans [Member] | Consumer Loans [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	2,078,286	1,991,910
Originated Loans [Member] | Consumer Loans [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	8,150	9,309
Originated Loans [Member] | Consumer Loans [Member] | Indirect [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	1,566,675	1,477,250
Originated Loans [Member] | Consumer Loans [Member] | Indirect [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	1,562,031	1,473,193
Originated Loans [Member] | Consumer Loans [Member] | Indirect [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	4,644	4,057
Originated Loans [Member] | Consumer Loans [Member] | Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	456,657	464,715
Originated Loans [Member] | Consumer Loans [Member] | Home Equity [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	453,278	459,540
Originated Loans [Member] | Consumer Loans [Member] | Home Equity [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	3,379	5,175
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	63,104	59,254
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	62,977	59,177
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	127	77
Originated Loans [Member] | Residential Real Estate Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	1,063,143	966,422
Originated Loans [Member] | Residential Real Estate Mortgages [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	1,055,055	958,013
Originated Loans [Member] | Residential Real Estate Mortgages [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	8,088	8,409
Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	500,094	611,514
Acquired Loans [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	237,618	285,729
Acquired Loans [Member] | Commercial Loans [Member] | Total Commercial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	186,736	235,934
Acquired Loans [Member] | Commercial Loans [Member] | Total Commercial and Agricultural [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	175,854	222,112
Acquired Loans [Member] | Commercial Loans [Member] | Total Commercial and Agricultural [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	1,307	2,976
Acquired Loans [Member] | Commercial Loans [Member] | Total Commercial and Agricultural [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	8,370	10,846
Acquired Loans [Member] | Commercial Loans [Member] | Total Commercial and Agricultural [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	1,205	0
Acquired Loans [Member] | Commercial Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	49,447	68,991
Acquired Loans [Member] | Commercial Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	48,194	67,241
Acquired Loans [Member] | Commercial Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	76	802
Acquired Loans [Member] | Commercial Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	1,177	948
Acquired Loans [Member] | Commercial Loans [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	0	0
Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	137,289	166,943
Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	127,660	154,871
Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	1,231	2,174
Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	7,193	9,898
Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	1,205	0
Acquired Loans [Member] | Commercial Loans [Member] | Business Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	50,882	49,795
Acquired Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | Non-classified [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	47,347	46,032
Acquired Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | Classified [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	3,535	3,763
Acquired Loans [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	63,005	95,427
Acquired Loans [Member] | Consumer Loans [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	62,671	94,822
Acquired Loans [Member] | Consumer Loans [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	334	605
Acquired Loans [Member] | Consumer Loans [Member] | Indirect [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	8,693	27,775
Acquired Loans [Member] | Consumer Loans [Member] | Indirect [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	8,646	27,670
Acquired Loans [Member] | Consumer Loans [Member] | Indirect [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	47	105
Acquired Loans [Member] | Consumer Loans [Member] | Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	51,127	63,727
Acquired Loans [Member] | Consumer Loans [Member] | Home Equity [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	50,860	63,270
Acquired Loans [Member] | Consumer Loans [Member] | Home Equity [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	267	457
Acquired Loans [Member] | Consumer Loans [Member] | Direct [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	3,185	3,925
Acquired Loans [Member] | Consumer Loans [Member] | Direct [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	3,165	3,882
Acquired Loans [Member] | Consumer Loans [Member] | Direct [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	20	43
Acquired Loans [Member] | Residential Real Estate Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	199,471	230,358
Acquired Loans [Member] | Residential Real Estate Mortgages [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	196,508	227,448
Acquired Loans [Member] | Residential Real Estate Mortgages [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Net Loans	$ 2,963	$ 2,910