Allowance for Loan Losses and Credit Quality of Loans, Credit Quality by Loan Class (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012 Commercial Credit Exposure [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Pass [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Pass [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Pass [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Special Mention [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Special Mention [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Special Mention [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Substandard [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Substandard [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Substandard [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Doubtful [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Doubtful [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Doubtful [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Non-classified [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Non-classified [Member] ACQUIRED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Classified [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Classified [Member] ACQUIRED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Commercial [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Commercial [Member] Pass [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] Pass [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] Pass [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Commercial [Member] Special Mention [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] Special Mention [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] Special Mention [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Commercial [Member] Substandard [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] Substandard [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] Substandard [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Commercial [Member] Doubtful [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] Doubtful [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] Doubtful [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Commercial Real Estate [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial Real Estate [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial Real Estate [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Commercial Real Estate [Member] Pass [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial Real Estate [Member] Pass [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial Real Estate [Member] Pass [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Commercial Real Estate [Member] Special Mention [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial Real Estate [Member] Special Mention [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial Real Estate [Member] Special Mention [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Commercial Real Estate [Member] Substandard [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial Real Estate [Member] Substandard [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial Real Estate [Member] Substandard [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Commercial Real Estate [Member] Doubtful [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial Real Estate [Member] Doubtful [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Commercial Real Estate [Member] Doubtful [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Agricultural [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Agricultural [Member] Pass [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] Pass [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] Pass [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Agricultural [Member] Special Mention [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] Special Mention [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] Special Mention [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Agricultural [Member] Substandard [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] Substandard [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] Substandard [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Agricultural [Member] Doubtful [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] Doubtful [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] Doubtful [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Agricultural Real Estate [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Agricultural Real Estate [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Agricultural Real Estate [Member] Pass [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Agricultural Real Estate [Member] Pass [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Agricultural Real Estate [Member] Special Mention [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Agricultural Real Estate [Member] Special Mention [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Agricultural Real Estate [Member] Substandard [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Agricultural Real Estate [Member] Substandard [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Agricultural Real Estate [Member] Doubtful [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Agricultural Real Estate [Member] Doubtful [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Business Banking [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Business Banking [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Business Banking [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Business Banking [Member] Non-classified [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Business Banking [Member] Non-classified [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Business Banking [Member] Non-classified [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Business Banking [Member] Classified [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Business Banking [Member] Classified [Member] ACQUIRED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Business Banking [Member] Classified [Member] ORIGINATED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Total Small Business Receivable [Member] ORIGINATED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Total Small Business Receivable [Member] Non-classified [Member] ORIGINATED [Member]	Sep. 30, 2013 Commercial Credit Exposure [Member] Total Small Business Receivable [Member] Classified [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] ACQUIRED [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Performing [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Performing [Member] ACQUIRED [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Performing [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Nonperforming [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Nonperforming [Member] ACQUIRED [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Nonperforming [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Indirect [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Indirect [Member] ACQUIRED [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Indirect [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Indirect [Member] Performing [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Indirect [Member] Performing [Member] ACQUIRED [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Indirect [Member] Performing [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Indirect [Member] Nonperforming [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Indirect [Member] Nonperforming [Member] ACQUIRED [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Indirect [Member] Nonperforming [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Home Equity Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Home Equity Member] ACQUIRED [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Home Equity Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Home Equity Member] Performing [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Home Equity Member] Performing [Member] ACQUIRED [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Home Equity Member] Performing [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Home Equity Member] Nonperforming [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Home Equity Member] Nonperforming [Member] ACQUIRED [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Home Equity Member] Nonperforming [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Direct [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Direct [Member] ACQUIRED [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Direct [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Direct [Member] Performing [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Direct [Member] Performing [Member] ACQUIRED [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Direct [Member] Performing [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Direct [Member] Nonperforming [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Direct [Member] Nonperforming [Member] ACQUIRED [Member]	Sep. 30, 2013 Consumer Credit Exposure [Member] Direct [Member] Nonperforming [Member] ORIGINATED [Member]	Dec. 31, 2012 Residential Mortgage Credit Exposure [Member]	Sep. 30, 2013 Residential Mortgage Credit Exposure [Member] ACQUIRED [Member]	Sep. 30, 2013 Residential Mortgage Credit Exposure [Member] ORIGINATED [Member]	Dec. 31, 2012 Residential Mortgage Credit Exposure [Member] Performing [Member]	Sep. 30, 2013 Residential Mortgage Credit Exposure [Member] Performing [Member] ACQUIRED [Member]	Sep. 30, 2013 Residential Mortgage Credit Exposure [Member] Performing [Member] ORIGINATED [Member]	Dec. 31, 2012 Residential Mortgage Credit Exposure [Member] Nonperforming [Member]	Sep. 30, 2013 Residential Mortgage Credit Exposure [Member] Nonperforming [Member] ACQUIRED [Member]	Sep. 30, 2013 Residential Mortgage Credit Exposure [Member] Nonperforming [Member] ORIGINATED [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	$ 1,637,411	$ 359,168	$ 1,613,509	$ 1,515,732	$ 319,905	$ 1,568,517	$ 50,552	$ 6,364	$ 10,580	$ 68,347	$ 32,899	$ 34,400	$ 2,780	$ 0	$ 12	$ 342,528	$ 68,917	$ 23,432	$ 4,721	$ 561,481	$ 114,374	$ 594,524	$ 522,985	$ 98,128	$ 574,229	$ 18,401	$ 1,602	$ 10,098	$ 17,351	$ 14,644	$ 10,197	$ 2,744	$ 0	$ 0	$ 974,795	$ 244,794	$ 919,254	$ 901,928	$ 221,777	$ 903,073	$ 32,135	$ 4,762	$ 50	$ 40,732	$ 18,255	$ 16,131	$ 0	$ 0	$ 0	$ 63,758	$ 0	$ 64,792	$ 57,347	$ 0	$ 59,797	$ 13	$ 0	$ 389	$ 6,362	$ 0	$ 4,594	$ 36	$ 0	$ 12	$ 37,377	$ 34,939	$ 33,472	$ 31,418	$ 3	$ 43	$ 3,902	$ 3,478	$ 0	$ 0	$ 365,960	$ 73,638	$ 332,533	$ 342,528	$ 68,917	$ 313,250	$ 23,432	$ 4,721	$ 19,283	$ 332,533	$ 313,250	$ 19,283	$ 1,623,138	$ 243,469	$ 1,716,756	$ 1,612,098	$ 242,599	$ 1,707,155	$ 11,040	$ 870	$ 9,601	$ 980,997	$ 144,520	$ 1,113,816	$ 978,235	$ 144,230	$ 1,111,147	$ 2,762	$ 290	$ 2,669	$ 575,282	$ 90,700	$ 542,322	$ 567,354	$ 90,193	$ 535,589	$ 7,928	$ 507	$ 6,733	$ 66,859	$ 8,249	$ 60,618	$ 66,509	$ 8,176	$ 60,419	$ 350	$ 73	$ 199	$ 651,107	$ 325,491	$ 702,667	$ 641,608	$ 321,631	$ 695,007	$ 9,499	$ 3,860	$ 7,660