Allowance for Loan Losses and Credit Quality of Loans, Past Due Loans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 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	$ 22,452	$ 31,961
61 - 90 Days Past Due Accruing	6,120	5,894
Greater Than 90 Days Past Due Accruing	2,700	3,737
Total Past Due Accruing	31,272	41,592
Non-Accrual	51,464	49,965
Current	5,399,289	5,315,238
Ending balance of loans	5,482,025	5,406,795
Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	19,966	28,124
61 - 90 Days Past Due Accruing	5,896	5,660
Greater Than 90 Days Past Due Accruing	2,523	3,657
Total Past Due Accruing	28,385	37,441
Non-Accrual	35,362	33,883
Current	4,523,180	4,405,079
Ending balance of loans	4,586,927	4,476,403
ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	2,486	3,837
61 - 90 Days Past Due Accruing	224	234
Greater Than 90 Days Past Due Accruing	177	80
Total Past Due Accruing	2,887	4,151
Non-Accrual	16,102	16,082
Current	876,109	910,159
Ending balance of loans	895,098	930,392
Commercial Loans [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Non-Accrual	19,758	19,300
Commercial Loans [Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Non-Accrual	11,007	11,498
Commercial Loans [Member] | Commercial [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	0	105
61 - 90 Days Past Due Accruing	409	247
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	409	352
Non-Accrual	3,644	3,669
Current	631,041	612,402
Ending balance of loans	635,094	616,423
Commercial Loans [Member] | Commercial [Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	150	24
61 - 90 Days Past Due Accruing	0	0
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	150	24
Non-Accrual	6,477	6,599
Current	97,406	96,603
Ending balance of loans	104,033	103,226
Commercial Loans [Member] | Commercial Real Estate [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	367	1,366
61 - 90 Days Past Due Accruing	69	0
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	436	1,366
Non-Accrual	7,282	7,834
Current	959,156	925,116
Ending balance of loans	966,874	934,316
Commercial Loans [Member] | Commercial Real Estate [Member] | ACQUIRED [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	3,493	3,559
Current	219,524	225,455
Ending balance of loans	223,017	229,014
Commercial Loans [Member] | Agricultural [Member] | Originated Loans [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	1,366	1,135
Current	60,979	63,856
Ending balance of loans	62,345	65,162
Commercial Loans [Member] | Agricultural Real Estate [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	136	519
61 - 90 Days Past Due Accruing	0	0
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	136	519
Non-Accrual	1,758	961
Current	36,719	35,172
Ending balance of loans	38,613	36,652
Commercial Loans [Member] | Business Banking [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	1,151	1,228
61 - 90 Days Past Due Accruing	159	122
Greater Than 90 Days Past Due Accruing	158	105
Total Past Due Accruing	1,468	1,455
Non-Accrual	5,708	5,701
Current	330,558	330,523
Ending balance of loans	337,734	337,679
Commercial Loans [Member] | Business Banking [Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	45	320
61 - 90 Days Past Due Accruing	0	2
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	45	322
Non-Accrual	1,037	1,340
Current	67,410	68,487
Ending balance of loans	68,492	70,149
Commercial Loans [Member] | Total Commercial Loan [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	1,654	3,368
61 - 90 Days Past Due Accruing	637	390
Greater Than 90 Days Past Due Accruing	158	105
Total Past Due Accruing	2,449	3,863
Non-Accrual	19,758	19,300
Current	2,018,453	1,967,069
Ending balance of loans	2,040,660	1,990,232
Commercial Loans [Member] | Total Commercial Loan [Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	195	344
61 - 90 Days Past Due Accruing	0	2
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	195	346
Non-Accrual	11,007	11,498
Current	384,340	390,545
Ending balance of loans	395,542	402,389
Consumer Loans [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Non-Accrual	8,699	7,478
Consumer Loans [Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Non-Accrual	975	712
Consumer Loans [Member] | Indirect [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	9,189	14,093
61 - 90 Days Past Due Accruing	2,061	2,878
Greater Than 90 Days Past Due Accruing	1,286	1,583
Total Past Due Accruing	12,536	18,554
Non-Accrual	1,549	1,461
Current	1,203,341	1,141,829
Ending balance of loans	1,217,426	1,161,844
Consumer Loans [Member] | Indirect [Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	575	939
61 - 90 Days Past Due Accruing	84	113
Greater Than 90 Days Past Due Accruing	50	71
Total Past Due Accruing	709	1,123
Non-Accrual	129	93
Current	107,501	123,870
Ending balance of loans	108,339	125,086
Consumer Loans [Member] | Home Equity Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	5,403	6,033
61 - 90 Days Past Due Accruing	2,032	1,888
Greater Than 90 Days Past Due Accruing	583	1,115
Total Past Due Accruing	8,018	9,036
Non-Accrual	7,074	5,931
Current	502,372	517,856
Ending balance of loans	517,464	532,823
Consumer Loans [Member] | Home Equity Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	288	753
61 - 90 Days Past Due Accruing	93	63
Greater Than 90 Days Past Due Accruing	112	0
Total Past Due Accruing	493	816
Non-Accrual	808	570
Current	83,044	85,690
Ending balance of loans	84,345	87,076
Consumer Loans [Member] | Direct [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	413	679
61 - 90 Days Past Due Accruing	90	125
Greater Than 90 Days Past Due Accruing	52	46
Total Past Due Accruing	555	850
Non-Accrual	76	86
Current	54,313	57,347
Ending balance of loans	54,944	58,283
Consumer Loans [Member] | Direct [Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	99	76
61 - 90 Days Past Due Accruing	8	56
Greater Than 90 Days Past Due Accruing	15	9
Total Past Due Accruing	122	141
Non-Accrual	38	49
Current	6,352	7,235
Ending balance of loans	6,512	7,425
Consumer Loans [Member] | Total Consumer Loan [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	15,005	20,805
61 - 90 Days Past Due Accruing	4,183	4,891
Greater Than 90 Days Past Due Accruing	1,921	2,744
Total Past Due Accruing	21,109	28,440
Non-Accrual	8,699	7,478
Current	1,760,026	1,717,032
Ending balance of loans	1,789,834	1,752,950
Consumer Loans [Member] | Total Consumer Loan [Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	962	1,768
61 - 90 Days Past Due Accruing	185	232
Greater Than 90 Days Past Due Accruing	177	80
Total Past Due Accruing	1,324	2,080
Non-Accrual	975	712
Current	196,897	216,795
Ending balance of loans	199,196	219,587
Residential Real Estate Mortgages [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	3,307	3,951
61 - 90 Days Past Due Accruing	1,076	379
Greater Than 90 Days Past Due Accruing	444	808
Total Past Due Accruing	4,827	5,138
Non-Accrual	6,905	7,105
Current	744,701	720,978
Ending balance of loans	756,433	733,221
Residential Real Estate Mortgages [Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	1,329	1,725
61 - 90 Days Past Due Accruing	39	0
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	1,368	1,725
Non-Accrual	4,120	3,872
Current	294,872	302,819
Ending balance of loans	$ 300,360	$ 308,416