Allowance for Loan Losses and Credit Quality of Loans, Past Due Loans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment, Aging [Abstract]
Minimum number of days past due for nonaccrual loan status (in days)	90 days
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		$ 22,852
61 - 90 Days Past Due Accruing		5,277
Greater Than 90 Days Past Due Accruing		2,448
Total Past Due Accruing		30,577
Non-Accrual		39,676
Current		4,207,363
Ending balance of loans	5,195,033	4,277,616
ORIGINATED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	22,561
61 - 90 Days Past Due Accruing	4,441
Greater Than 90 Days Past Due Accruing	1,527
Total Past Due Accruing	28,529
Non-Accrual	36,953
Current	4,006,418
Ending balance of loans	4,071,900
ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	12,021
61 - 90 Days Past Due Accruing	1,284
Greater Than 90 Days Past Due Accruing	124
Total Past Due Accruing	13,429
Non-Accrual	4,773
Current	1,104,931
Ending balance of loans	1,123,133
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Ending balance of loans	2,306,954	2,003,371
Commercial Loans [Member] | ORIGINATED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	5,269
61 - 90 Days Past Due Accruing	766
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	6,035
Non-Accrual	19,599
Current	1,814,647
Ending balance of loans	1,840,281
Commercial Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		0
61 - 90 Days Past Due Accruing		0
Greater Than 90 Days Past Due Accruing		0
Total Past Due Accruing		0
Non-Accrual		4,985
Current		556,496
Ending balance of loans		561,481
Commercial Loans [Member] | Commercial [Member] | ORIGINATED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	549
61 - 90 Days Past Due Accruing	0
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	549
Non-Accrual	3,098
Current	545,847
Ending balance of loans	549,494
Commercial Loans [Member] | Commercial [Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	1,037
61 - 90 Days Past Due Accruing	124
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	1,161
Non-Accrual	76
Current	132,082
Ending balance of loans	133,319
Commercial Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		126
61 - 90 Days Past Due Accruing		0
Greater Than 90 Days Past Due Accruing		0
Total Past Due Accruing		126
Non-Accrual		7,977
Current		966,692
Ending balance of loans		974,795
Commercial Loans [Member] | Commercial Real Estate [Member] | ORIGINATED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	1,753
61 - 90 Days Past Due Accruing	0
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	1,753
Non-Accrual	7,766
Current	849,715
Ending balance of loans	859,234
Commercial Loans [Member] | Commercial Real Estate [Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	1,484
61 - 90 Days Past Due Accruing	456
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	1,940
Non-Accrual	0
Current	242,561
Ending balance of loans	244,501
Commercial Loans [Member] | Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		22
61 - 90 Days Past Due Accruing		0
Greater Than 90 Days Past Due Accruing		0
Total Past Due Accruing		22
Non-Accrual		699
Current		63,037
Ending balance of loans		63,758
Commercial Loans [Member] | Agricultural [Member] | ORIGINATED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	111
61 - 90 Days Past Due Accruing	49
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	160
Non-Accrual	728
Current	60,297
Ending balance of loans	61,185
Commercial Loans [Member] | Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		108
61 - 90 Days Past Due Accruing		0
Greater Than 90 Days Past Due Accruing		103
Total Past Due Accruing		211
Non-Accrual		1,038
Current		36,128
Ending balance of loans		37,377
Commercial Loans [Member] | Agricultural Real Estate [Member] | ORIGINATED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	39
61 - 90 Days Past Due Accruing	0
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	39
Non-Accrual	1,164
Current	33,136
Ending balance of loans	34,339
Commercial Loans [Member] | Business Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		3,019
61 - 90 Days Past Due Accruing		708
Greater Than 90 Days Past Due Accruing		45
Total Past Due Accruing		3,772
Non-Accrual		6,738
Current		355,450
Ending balance of loans		365,960
Commercial Loans [Member] | Business Banking [Member] | ORIGINATED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	2,817
61 - 90 Days Past Due Accruing	717
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	3,534
Non-Accrual	6,843
Current	325,652
Ending balance of loans	336,029
Commercial Loans [Member] | Business Banking [Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	1,663
61 - 90 Days Past Due Accruing	241
Greater Than 90 Days Past Due Accruing	6
Total Past Due Accruing	1,910
Non-Accrual	1,266
Current	85,677
Ending balance of loans	88,853
Commercial Loans [Member] | Total Commercial Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		3,275
61 - 90 Days Past Due Accruing		708
Greater Than 90 Days Past Due Accruing		148
Total Past Due Accruing		4,131
Non-Accrual		21,437
Current		1,977,803
Ending balance of loans		2,003,371
Commercial Loans [Member] | Total Commercial Loan [Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	4,184
61 - 90 Days Past Due Accruing	821
Greater Than 90 Days Past Due Accruing	6
Total Past Due Accruing	5,011
Non-Accrual	1,342
Current	460,320
Ending balance of loans	466,673
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Ending balance of loans	1,891,154	1,623,138
Consumer Loans [Member] | Indirect [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		10,956
61 - 90 Days Past Due Accruing		2,477
Greater Than 90 Days Past Due Accruing		1,205
Total Past Due Accruing		14,638
Non-Accrual		1,557
Current		964,802
Ending balance of loans		980,997
Consumer Loans [Member] | Indirect [Member] | ORIGINATED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	8,783
61 - 90 Days Past Due Accruing	1,667
Greater Than 90 Days Past Due Accruing	863
Total Past Due Accruing	11,313
Non-Accrual	1,782
Current	981,043
Ending balance of loans	994,138
Consumer Loans [Member] | Indirect [Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	833
61 - 90 Days Past Due Accruing	18
Greater Than 90 Days Past Due Accruing	41
Total Past Due Accruing	892
Non-Accrual	168
Current	186,677
Ending balance of loans	187,737
Consumer Loans [Member] | Home Equity Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		6,065
61 - 90 Days Past Due Accruing		1,223
Greater Than 90 Days Past Due Accruing		681
Total Past Due Accruing		7,969
Non-Accrual		7,247
Current		560,066
Ending balance of loans		575,282
Consumer Loans [Member] | Home Equity Member] | ORIGINATED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	4,811
61 - 90 Days Past Due Accruing	1,450
Greater Than 90 Days Past Due Accruing	533
Total Past Due Accruing	6,794
Non-Accrual	7,241
Current	525,902
Ending balance of loans	539,937
Consumer Loans [Member] | Home Equity Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	961
61 - 90 Days Past Due Accruing	273
Greater Than 90 Days Past Due Accruing	67
Total Past Due Accruing	1,301
Non-Accrual	465
Current	95,806
Ending balance of loans	97,572
Consumer Loans [Member] | Direct [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		717
61 - 90 Days Past Due Accruing		144
Greater Than 90 Days Past Due Accruing		84
Total Past Due Accruing		945
Non-Accrual		266
Current		65,648
Ending balance of loans		66,859
Consumer Loans [Member] | Direct [Member] | ORIGINATED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	449
61 - 90 Days Past Due Accruing	87
Greater Than 90 Days Past Due Accruing	52
Total Past Due Accruing	588
Non-Accrual	270
Current	61,441
Ending balance of loans	62,299
Consumer Loans [Member] | Direct [Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	63
61 - 90 Days Past Due Accruing	2
Greater Than 90 Days Past Due Accruing	10
Total Past Due Accruing	75
Non-Accrual	85
Current	9,311
Ending balance of loans	9,471
Consumer Loans [Member] | Total Consumer Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		17,738
61 - 90 Days Past Due Accruing		3,844
Greater Than 90 Days Past Due Accruing		1,970
Total Past Due Accruing		23,552
Non-Accrual		9,070
Current		1,590,516
Ending balance of loans		1,623,138
Consumer Loans [Member] | Total Consumer Loan [Member] | ORIGINATED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	14,043
61 - 90 Days Past Due Accruing	3,204
Greater Than 90 Days Past Due Accruing	1,448
Total Past Due Accruing	18,695
Non-Accrual	9,293
Current	1,568,386
Ending balance of loans	1,596,374
Consumer Loans [Member] | Total Consumer Loan [Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	1,857
61 - 90 Days Past Due Accruing	293
Greater Than 90 Days Past Due Accruing	118
Total Past Due Accruing	2,268
Non-Accrual	718
Current	291,794
Ending balance of loans	294,780
Residential Real Estate Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		1,839
61 - 90 Days Past Due Accruing		725
Greater Than 90 Days Past Due Accruing		330
Total Past Due Accruing		2,894
Non-Accrual		9,169
Current		639,044
Ending balance of loans	996,925	651,107
Residential Real Estate Mortgages [Member] | ORIGINATED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	3,249
61 - 90 Days Past Due Accruing	471
Greater Than 90 Days Past Due Accruing	79
Total Past Due Accruing	3,799
Non-Accrual	8,061
Current	623,385
Ending balance of loans	635,245
Residential Real Estate Mortgages [Member] | ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	5,980
61 - 90 Days Past Due Accruing	170
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	6,150
Non-Accrual	2,713
Current	352,817
Ending balance of loans	$ 361,680