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]	Jun. 30, 2013 Commercial Credit Exposure [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Pass [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Pass [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Pass [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Special Mention [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Special Mention [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Special Mention [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Substandard [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Substandard [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Substandard [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Doubtful [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Doubtful [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Doubtful [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Non-classified [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Non-classified [Member] ACQUIRED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Classified [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Classified [Member] ACQUIRED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Commercial [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Commercial [Member] Pass [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] Pass [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] Pass [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Commercial [Member] Special Mention [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] Special Mention [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] Special Mention [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Commercial [Member] Substandard [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] Substandard [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] Substandard [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Commercial [Member] Doubtful [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] Doubtful [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Commercial [Member] Doubtful [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Commercial Real Estate [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Commercial Real Estate [Member] ACQUIRED [Member]	Jun. 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]	Jun. 30, 2013 Commercial Credit Exposure [Member] Commercial Real Estate [Member] Pass [Member] ACQUIRED [Member]	Jun. 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]	Jun. 30, 2013 Commercial Credit Exposure [Member] Commercial Real Estate [Member] Special Mention [Member] ACQUIRED [Member]	Jun. 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]	Jun. 30, 2013 Commercial Credit Exposure [Member] Commercial Real Estate [Member] Substandard [Member] ACQUIRED [Member]	Jun. 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]	Jun. 30, 2013 Commercial Credit Exposure [Member] Commercial Real Estate [Member] Doubtful [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Commercial Real Estate [Member] Doubtful [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Agricultural [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Agricultural [Member] Pass [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] Pass [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] Pass [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Agricultural [Member] Special Mention [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] Special Mention [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] Special Mention [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Agricultural [Member] Substandard [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] Substandard [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] Substandard [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Agricultural [Member] Doubtful [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] Doubtful [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Agricultural [Member] Doubtful [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Agricultural Real Estate [Member]	Jun. 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]	Jun. 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]	Jun. 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]	Jun. 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]	Jun. 30, 2013 Commercial Credit Exposure [Member] Agricultural Real Estate [Member] Doubtful [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Business Banking [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Business Banking [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Business Banking [Member] ORIGINATED [Member]	Dec. 31, 2012 Commercial Credit Exposure [Member] Business Banking [Member] Non-classified [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Business Banking [Member] Non-classified [Member] ACQUIRED [Member]	Jun. 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]	Jun. 30, 2013 Commercial Credit Exposure [Member] Business Banking [Member] Classified [Member] ACQUIRED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Business Banking [Member] Classified [Member] ORIGINATED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Total Small Business Receivable [Member] ORIGINATED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Total Small Business Receivable [Member] Non-classified [Member] ORIGINATED [Member]	Jun. 30, 2013 Commercial Credit Exposure [Member] Total Small Business Receivable [Member] Classified [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] ACQUIRED [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Performing [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Performing [Member] ACQUIRED [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Performing [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Nonperforming [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Nonperforming [Member] ACQUIRED [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Nonperforming [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Indirect [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Indirect [Member] ACQUIRED [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Indirect [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Indirect [Member] Performing [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Indirect [Member] Performing [Member] ACQUIRED [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Indirect [Member] Performing [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Indirect [Member] Nonperforming [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Indirect [Member] Nonperforming [Member] ACQUIRED [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Indirect [Member] Nonperforming [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Home Equity Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Home Equity Member] ACQUIRED [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Home Equity Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Home Equity Member] Performing [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Home Equity Member] Performing [Member] ACQUIRED [Member]	Jun. 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]	Jun. 30, 2013 Consumer Credit Exposure [Member] Home Equity Member] Nonperforming [Member] ACQUIRED [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Home Equity Member] Nonperforming [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Direct [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Direct [Member] ACQUIRED [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Direct [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Direct [Member] Performing [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Direct [Member] Performing [Member] ACQUIRED [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Direct [Member] Performing [Member] ORIGINATED [Member]	Dec. 31, 2012 Consumer Credit Exposure [Member] Direct [Member] Nonperforming [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Direct [Member] Nonperforming [Member] ACQUIRED [Member]	Jun. 30, 2013 Consumer Credit Exposure [Member] Direct [Member] Nonperforming [Member] ORIGINATED [Member]	Dec. 31, 2012 Residential Mortgage Credit Exposure [Member]	Jun. 30, 2013 Residential Mortgage Credit Exposure [Member] ACQUIRED [Member]	Jun. 30, 2013 Residential Mortgage Credit Exposure [Member] ORIGINATED [Member]	Dec. 31, 2012 Residential Mortgage Credit Exposure [Member] Performing [Member]	Jun. 30, 2013 Residential Mortgage Credit Exposure [Member] Performing [Member] ACQUIRED [Member]	Jun. 30, 2013 Residential Mortgage Credit Exposure [Member] Performing [Member] ORIGINATED [Member]	Dec. 31, 2012 Residential Mortgage Credit Exposure [Member] Nonperforming [Member]	Jun. 30, 2013 Residential Mortgage Credit Exposure [Member] Nonperforming [Member] ACQUIRED [Member]	Jun. 30, 2013 Residential Mortgage Credit Exposure [Member] Nonperforming [Member] ORIGINATED [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	$ 1,637,411	$ 380,486	$ 1,570,715	$ 1,515,732	$ 342,057	$ 1,510,121	$ 50,552	$ 17,145	$ 13,637	$ 68,347	$ 21,284	$ 45,668	$ 2,780	$ 0	$ 1,289	$ 342,528	$ 75,418	$ 23,432	$ 5,091	$ 561,481	$ 138,139	$ 585,938	$ 522,985	$ 121,901	$ 566,686	$ 18,401	$ 8,323	$ 1,899	$ 17,351	$ 7,915	$ 16,850	$ 2,744	$ 0	$ 503	$ 974,795	$ 242,322	$ 887,963	$ 901,928	$ 220,131	$ 855,687	$ 32,135	$ 8,822	$ 11,657	$ 40,732	$ 13,369	$ 19,856	$ 0	$ 0	$ 763	$ 63,758	$ 25	$ 64,603	$ 57,347	$ 25	$ 59,026	$ 13	$ 0	$ 78	$ 6,362	$ 0	$ 5,476	$ 36	$ 0	$ 23	$ 37,377	$ 32,211	$ 33,472	$ 28,722	$ 3	$ 3	$ 3,902	$ 3,486	$ 0	$ 0	$ 365,960	$ 80,509	$ 337,187	$ 342,528	$ 75,418	$ 317,362	$ 23,432	$ 5,091	$ 19,825	$ 337,187	$ 317,362	$ 19,825	$ 1,623,138	$ 269,151	$ 1,651,020	$ 1,612,098	$ 267,949	$ 1,641,427	$ 11,040	$ 1,202	$ 9,593	$ 980,997	$ 165,342	$ 1,049,044	$ 978,235	$ 165,180	$ 1,046,911	$ 2,762	$ 162	$ 2,133	$ 575,282	$ 94,894	$ 540,389	$ 567,354	$ 94,006	$ 533,102	$ 7,928	$ 888	$ 7,287	$ 66,859	$ 8,915	$ 61,587	$ 66,509	$ 8,763	$ 61,414	$ 350	$ 152	$ 173	$ 651,107	$ 338,750	$ 662,892	$ 641,608	$ 335,887	$ 656,120	$ 9,499	$ 2,863	$ 6,772