Allowance for Loan Losses and Credit Quality of Loans, Past Due Loans (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment, Aging [Abstract]
Minimum number of days past due for nonaccrual loan status	90 days
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	$ 27,402	$ 31,961
61 - 90 Days Past Due Accruing	6,150	5,894
Greater Than 90 Days Past Due Accruing	4,941	3,737
Total Past Due Accruing	38,493	41,592
Non-Accrual	41,074	49,965
Current	5,515,704	5,315,238
Recorded Total Loans and Leases	5,595,271	5,406,795
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Recorded Total Loans and Leases	2,473,702	2,392,621
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Recorded Total Loans and Leases	2,005,980	1,972,537
Residential Real Estate Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Recorded Total Loans and Leases	1,115,589	1,041,637
Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	25,496	28,124
61 - 90 Days Past Due Accruing	5,805	5,660
Greater Than 90 Days Past Due Accruing	4,204	3,657
Total Past Due Accruing	35,505	37,441
Non-Accrual	30,845	33,883
Current	4,781,587	4,405,079
Recorded Total Loans and Leases	4,847,937	4,476,403
Originated Loans [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	1,010	3,368
61 - 90 Days Past Due Accruing	970	390
Greater Than 90 Days Past Due Accruing	84	105
Total Past Due Accruing	2,064	3,863
Non-Accrual	13,431	19,300
Current	2,124,876	1,967,069
Recorded Total Loans and Leases	2,140,371	1,990,232
Originated Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	0	105
61 - 90 Days Past Due Accruing	735	247
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	735	352
Non-Accrual	1,012	3,669
Current	613,400	612,402
Recorded Total Loans and Leases	615,147	616,423
Originated Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	192	1,366
61 - 90 Days Past Due Accruing	0	0
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	192	1,366
Non-Accrual	4,127	7,834
Current	1,064,549	925,116
Recorded Total Loans and Leases	1,068,868	934,316
Originated Loans [Member] | Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	0	150
61 - 90 Days Past Due Accruing	0	21
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	0	171
Non-Accrual	817	1,135
Current	32,130	63,856
Recorded Total Loans and Leases	32,947	65,162
Originated Loans [Member] | Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	19	519
61 - 90 Days Past Due Accruing	0	0
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	19	519
Non-Accrual	565	961
Current	24,390	35,172
Recorded Total Loans and Leases	24,974	36,652
Originated Loans [Member] | Business Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	799	1,228
61 - 90 Days Past Due Accruing	235	122
Greater Than 90 Days Past Due Accruing	84	105
Total Past Due Accruing	1,118	1,455
Non-Accrual	6,910	5,701
Current	390,407	330,523
Recorded Total Loans and Leases	398,435	337,679
Originated Loans [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	21,585	20,805
61 - 90 Days Past Due Accruing	4,739	4,891
Greater Than 90 Days Past Due Accruing	2,864	2,744
Total Past Due Accruing	29,188	28,440
Non-Accrual	8,644	7,478
Current	1,820,892	1,717,032
Recorded Total Loans and Leases	1,858,724	1,752,950
Originated Loans [Member] | Indirect [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	16,434	14,093
61 - 90 Days Past Due Accruing	3,154	2,878
Greater Than 90 Days Past Due Accruing	1,991	1,583
Total Past Due Accruing	21,579	18,554
Non-Accrual	1,964	1,461
Current	1,286,507	1,141,829
Recorded Total Loans and Leases	1,310,050	1,161,844
Originated Loans [Member] | Home Equity Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	4,591	6,033
61 - 90 Days Past Due Accruing	1,428	1,888
Greater Than 90 Days Past Due Accruing	821	1,115
Total Past Due Accruing	6,840	9,036
Non-Accrual	6,596	5,931
Current	479,444	517,856
Recorded Total Loans and Leases	492,880	532,823
Originated Loans [Member] | Direct [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	560	679
61 - 90 Days Past Due Accruing	157	125
Greater Than 90 Days Past Due Accruing	52	46
Total Past Due Accruing	769	850
Non-Accrual	84	86
Current	54,941	57,347
Recorded Total Loans and Leases	55,794	58,283
Originated Loans [Member] | Residential Real Estate Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	2,901	3,951
61 - 90 Days Past Due Accruing	96	379
Greater Than 90 Days Past Due Accruing	1,256	808
Total Past Due Accruing	4,253	5,138
Non-Accrual	8,770	7,105
Current	835,819	720,978
Recorded Total Loans and Leases	848,842	733,221
Acquired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	1,906	3,837
61 - 90 Days Past Due Accruing	345	234
Greater Than 90 Days Past Due Accruing	737	80
Total Past Due Accruing	2,988	4,151
Non-Accrual	10,229	16,082
Current	734,117	910,159
Recorded Total Loans and Leases	747,334	930,392
Acquired Loans [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	5	344
61 - 90 Days Past Due Accruing	15	2
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	20	346
Non-Accrual	6,340	11,498
Current	326,971	390,545
Recorded Total Loans and Leases	333,331	402,389
Acquired Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	0	24
61 - 90 Days Past Due Accruing	0	0
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	0	24
Non-Accrual	3,009	6,599
Current	72,255	96,603
Recorded Total Loans and Leases	75,264	103,226
Acquired Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	0	0
61 - 90 Days Past Due Accruing	0	0
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	0	0
Non-Accrual	2,666	3,559
Current	197,222	225,455
Recorded Total Loans and Leases	199,888	229,014
Acquired Loans [Member] | Business Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	5	320
61 - 90 Days Past Due Accruing	15	2
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	20	322
Non-Accrual	665	1,340
Current	57,494	68,487
Recorded Total Loans and Leases	58,179	70,149
Acquired Loans [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	739	1,768
61 - 90 Days Past Due Accruing	65	232
Greater Than 90 Days Past Due Accruing	66	80
Total Past Due Accruing	870	2,080
Non-Accrual	696	712
Current	145,690	216,795
Recorded Total Loans and Leases	147,256	219,587
Acquired Loans [Member] | Indirect [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	518	939
61 - 90 Days Past Due Accruing	5	113
Greater Than 90 Days Past Due Accruing	54	71
Total Past Due Accruing	577	1,123
Non-Accrual	106	93
Current	64,540	123,870
Recorded Total Loans and Leases	65,223	125,086
Acquired Loans [Member] | Home Equity Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	190	753
61 - 90 Days Past Due Accruing	60	63
Greater Than 90 Days Past Due Accruing	5	0
Total Past Due Accruing	255	816
Non-Accrual	557	570
Current	75,904	85,690
Recorded Total Loans and Leases	76,716	87,076
Acquired Loans [Member] | Direct [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	31	76
61 - 90 Days Past Due Accruing	0	56
Greater Than 90 Days Past Due Accruing	7	9
Total Past Due Accruing	38	141
Non-Accrual	33	49
Current	5,246	7,235
Recorded Total Loans and Leases	5,317	7,425
Acquired Loans [Member] | Residential Real Estate Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	1,162	1,725
61 - 90 Days Past Due Accruing	265	0
Greater Than 90 Days Past Due Accruing	671	0
Total Past Due Accruing	2,098	1,725
Non-Accrual	3,193	3,872
Current	261,456	302,819
Recorded Total Loans and Leases	$ 266,747	$ 308,416