Allowance for Loan Losses and Credit Quality of Loans, Past Due Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Aging [Abstract]
Minimum number of days past due for nonaccrual loan status	90 days
Total Past Due Accruing	$ 39,485	$ 36,724
Non-Accrual	35,712	33,744
Current	6,122,860	5,812,665
Recorded Total Loans	6,198,057	5,883,133
31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	28,717	26,957
61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	5,958	6,105
Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	4,810	3,662
Commercial [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Recorded Total Loans	1,242,701	1,159,089
Home Equity [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Recorded Total Loans	507,784	528,442
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Recorded Total Loans	2,786,002	2,589,707
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Recorded Total Loans	2,149,441	2,096,646
Residential Real Estate Mortgages [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Recorded Total Loans	1,262,614	1,196,780
Originated Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	37,811	33,664
Non-Accrual	30,077	28,936
Current	5,630,075	5,209,019
Recorded Total Loans	5,697,963	5,271,619
Originated Loans [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	27,488	24,680
Originated Loans [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	5,870	5,649
Originated Loans [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	4,453	3,335
Originated Loans [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	1,965	2,276
Non-Accrual	18,292	14,553
Current	2,528,127	2,287,149
Recorded Total Loans	2,548,384	2,303,978
Originated Loans [Member] | Commercial Loans [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	1,642	1,827
Originated Loans [Member] | Commercial Loans [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	323	449
Originated Loans [Member] | Commercial Loans [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Originated Loans [Member] | Commercial Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	38	805
Non-Accrual	2,964	2,817
Current	650,568	640,696
Recorded Total Loans	653,570	644,318
Originated Loans [Member] | Commercial Loans [Member] | Commercial [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	33	782
Originated Loans [Member] | Commercial Loans [Member] | Commercial [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	5	23
Originated Loans [Member] | Commercial Loans [Member] | Commercial [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Originated Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	71
Non-Accrual	7,935	5,546
Current	1,343,854	1,189,280
Recorded Total Loans	1,351,789	1,194,897
Originated Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	39
Originated Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	32
Originated Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Originated Loans [Member] | Commercial Loans [Member] | Agricultural [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	94
Non-Accrual	730	897
Current	37,186	33,633
Recorded Total Loans	37,916	34,624
Originated Loans [Member] | Commercial Loans [Member] | Agricultural [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	94
Originated Loans [Member] | Commercial Loans [Member] | Agricultural [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Originated Loans [Member] | Commercial Loans [Member] | Agricultural [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Originated Loans [Member] | Commercial Loans [Member] | Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Non-Accrual	1,803	1,046
Current	30,619	28,172
Recorded Total Loans	32,422	29,218
Originated Loans [Member] | Commercial Loans [Member] | Agricultural Real Estate [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Originated Loans [Member] | Commercial Loans [Member] | Agricultural Real Estate [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Originated Loans [Member] | Commercial Loans [Member] | Agricultural Real Estate [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	1,927	1,306
Non-Accrual	4,860	4,247
Current	465,900	395,368
Recorded Total Loans	472,687	400,921
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	1,609	912
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	318	394
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Originated Loans [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	31,543	27,026
Non-Accrual	5,103	6,670
Current	2,049,790	1,967,523
Recorded Total Loans	2,086,436	2,001,219
Originated Loans [Member] | Consumer Loans [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	23,121	19,552
Originated Loans [Member] | Consumer Loans [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	5,375	4,835
Originated Loans [Member] | Consumer Loans [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	3,047	2,639
Originated Loans [Member] | Consumer Loans [Member] | Indirect [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	25,937	20,965
Non-Accrual	2,145	1,786
Current	1,538,593	1,454,499
Recorded Total Loans	1,566,675	1,477,250
Originated Loans [Member] | Consumer Loans [Member] | Indirect [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	19,253	15,731
Originated Loans [Member] | Consumer Loans [Member] | Indirect [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	4,185	2,963
Originated Loans [Member] | Consumer Loans [Member] | Indirect [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	2,499	2,271
Originated Loans [Member] | Consumer Loans [Member] | Home Equity [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	5,009	5,407
Non-Accrual	2,851	4,835
Current	448,797	454,473
Recorded Total Loans	456,657	464,715
Originated Loans [Member] | Consumer Loans [Member] | Home Equity [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	3,416	3,396
Originated Loans [Member] | Consumer Loans [Member] | Home Equity [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	1,065	1,671
Originated Loans [Member] | Consumer Loans [Member] | Home Equity [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	528	340
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	597	654
Non-Accrual	107	49
Current	62,400	58,551
Recorded Total Loans	63,104	59,254
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	452	425
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	125	201
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	20	28
Originated Loans [Member] | Residential Real Estate Mortgages [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	4,303	4,362
Non-Accrual	6,682	7,713
Current	1,052,158	954,347
Recorded Total Loans	1,063,143	966,422
Originated Loans [Member] | Residential Real Estate Mortgages [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	2,725	3,301
Originated Loans [Member] | Residential Real Estate Mortgages [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	172	365
Originated Loans [Member] | Residential Real Estate Mortgages [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	1,406	696
Acquired Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	1,674	3,060
Non-Accrual	5,635	4,808
Current	492,785	603,646
Recorded Total Loans	500,094	611,514
Acquired Loans [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	1,229	2,277
Acquired Loans [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	88	456
Acquired Loans [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	357	327
Acquired Loans [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	236	288
Non-Accrual	2,695	1,620
Current	234,687	283,821
Recorded Total Loans	237,618	285,729
Acquired Loans [Member] | Commercial Loans [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	236	288
Acquired Loans [Member] | Commercial Loans [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Acquired Loans [Member] | Commercial Loans [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Acquired Loans [Member] | Commercial Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Non-Accrual	0	0
Current	49,447	68,991
Recorded Total Loans	49,447	68,991
Acquired Loans [Member] | Commercial Loans [Member] | Commercial [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Acquired Loans [Member] | Commercial Loans [Member] | Commercial [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Acquired Loans [Member] | Commercial Loans [Member] | Commercial [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Non-Accrual	1,891	1,313
Current	135,398	165,630
Recorded Total Loans	137,289	166,943
Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Acquired Loans [Member] | Commercial Loans [Member] | Business Banking [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	236	288
Non-Accrual	804	307
Current	49,842	49,200
Recorded Total Loans	50,882	49,795
Acquired Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	236	288
Acquired Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Acquired Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Acquired Loans [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	474	710
Non-Accrual	304	604
Current	62,227	94,113
Recorded Total Loans	63,005	95,427
Acquired Loans [Member] | Consumer Loans [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	384	546
Acquired Loans [Member] | Consumer Loans [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	60	163
Acquired Loans [Member] | Consumer Loans [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	30	1
Acquired Loans [Member] | Consumer Loans [Member] | Indirect [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	105	155
Non-Accrual	47	104
Current	8,541	27,516
Recorded Total Loans	8,693	27,775
Acquired Loans [Member] | Consumer Loans [Member] | Indirect [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	100	143
Acquired Loans [Member] | Consumer Loans [Member] | Indirect [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	5	11
Acquired Loans [Member] | Consumer Loans [Member] | Indirect [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	1
Acquired Loans [Member] | Consumer Loans [Member] | Home Equity [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	337	459
Non-Accrual	237	457
Current	50,553	62,811
Recorded Total Loans	51,127	63,727
Acquired Loans [Member] | Consumer Loans [Member] | Home Equity [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	254	327
Acquired Loans [Member] | Consumer Loans [Member] | Home Equity [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	53	132
Acquired Loans [Member] | Consumer Loans [Member] | Home Equity [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	30	0
Acquired Loans [Member] | Consumer Loans [Member] | Direct [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	32	96
Non-Accrual	20	43
Current	3,133	3,786
Recorded Total Loans	3,185	3,925
Acquired Loans [Member] | Consumer Loans [Member] | Direct [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	30	76
Acquired Loans [Member] | Consumer Loans [Member] | Direct [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	2	20
Acquired Loans [Member] | Consumer Loans [Member] | Direct [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	0	0
Acquired Loans [Member] | Residential Real Estate Mortgages [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	964	2,062
Non-Accrual	2,636	2,584
Current	195,871	225,712
Recorded Total Loans	199,471	230,358
Acquired Loans [Member] | Residential Real Estate Mortgages [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	609	1,443
Acquired Loans [Member] | Residential Real Estate Mortgages [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	28	293
Acquired Loans [Member] | Residential Real Estate Mortgages [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	$ 327	$ 326