Allowance for Loan Losses and Credit Quality of Loans, Past Due Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	$ 29,880	$ 36,724
Non-Accrual	38,944	33,744
Current	5,898,985	5,812,665
Recorded Total Loans	5,967,809	5,883,133
31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	22,263	26,957
61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	5,432	6,105
Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	2,185	3,662
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Recorded Total Loans	2,617,111	2,589,707
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Recorded Total Loans	2,138,877	2,096,646
Residential Real Estate Mortgages [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Recorded Total Loans	1,211,821	1,196,780
Originated Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	27,365	33,664
Non-Accrual	34,149	28,936
Current	5,315,373	5,209,019
Recorded Total Loans	5,376,887	5,271,619
Originated Loans [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	20,434	24,680
Originated Loans [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	4,830	5,649
Originated Loans [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	2,101	3,335
Originated Loans [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	3,184	2,276
Non-Accrual	21,722	14,553
Current	2,312,575	2,287,149
Recorded Total Loans	2,337,481	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	2,483	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	701	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	616	805
Non-Accrual	2,903	2,817
Current	652,992	640,696
Recorded Total Loans	656,511	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	616	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	0	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	734	71
Non-Accrual	13,207	5,546
Current	1,202,805	1,189,280
Recorded Total Loans	1,216,746	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	73	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	661	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	952	897
Current	33,431	33,633
Recorded Total Loans	34,383	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	479	1,046
Current	29,440	28,172
Recorded Total Loans	29,919	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	1,834	1,306
Non-Accrual	4,181	4,247
Current	393,907	395,368
Recorded Total Loans	399,922	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	1,794	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	40	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	21,032	27,026
Non-Accrual	5,435	6,670
Current	2,026,101	1,967,523
Recorded Total Loans	2,052,568	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	15,756	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	3,336	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	1,940	2,639
Originated Loans [Member] | Consumer Loans [Member] | Indirect [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	16,539	20,965
Non-Accrual	1,582	1,786
Current	1,518,228	1,454,499
Recorded Total Loans	1,536,349	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	12,305	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	2,600	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	1,634	2,271
Originated Loans [Member] | Consumer Loans [Member] | Home Equity [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	3,942	5,407
Non-Accrual	3,743	4,835
Current	449,595	454,473
Recorded Total Loans	457,280	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	3,083	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	618	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	241	340
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	551	654
Non-Accrual	110	49
Current	58,278	58,551
Recorded Total Loans	58,939	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	368	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	118	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	65	28
Originated Loans [Member] | Residential Real Estate Mortgages [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	3,149	4,362
Non-Accrual	6,992	7,713
Current	976,697	954,347
Recorded Total Loans	986,838	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	2,195	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	793	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	161	696
Acquired Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	2,515	3,060
Non-Accrual	4,795	4,808
Current	583,612	603,646
Recorded Total Loans	590,922	611,514
Acquired Loans [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	1,829	2,277
Acquired Loans [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	602	456
Acquired Loans [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	84	327
Acquired Loans [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	463	288
Non-Accrual	1,730	1,620
Current	277,437	283,821
Recorded Total Loans	279,630	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	463	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	65,412	68,991
Recorded Total Loans	65,412	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	1,314	1,313
Current	167,131	165,630
Recorded Total Loans	168,445	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	463	288
Non-Accrual	416	307
Current	44,894	49,200
Recorded Total Loans	45,773	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	463	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	489	710
Non-Accrual	484	604
Current	85,336	94,113
Recorded Total Loans	86,309	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	444	546
Acquired Loans [Member] | Consumer Loans [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	34	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	11	1
Acquired Loans [Member] | Consumer Loans [Member] | Indirect [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	79	155
Non-Accrual	79	104
Current	21,689	27,516
Recorded Total Loans	21,847	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	71	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	7	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	1	1
Acquired Loans [Member] | Consumer Loans [Member] | Home Equity [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	389	459
Non-Accrual	340	457
Current	60,199	62,811
Recorded Total Loans	60,928	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	359	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	20	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	10	0
Acquired Loans [Member] | Consumer Loans [Member] | Direct [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due Accruing	21	96
Non-Accrual	65	43
Current	3,448	3,786
Recorded Total Loans	3,534	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	14	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	7	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	1,563	2,062
Non-Accrual	2,581	2,584
Current	220,839	225,712
Recorded Total Loans	224,983	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	922	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	568	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	$ 73	$ 326