Allowance for Loan and Lease Losses and Credit Quality of Loans and Leases Quality Indicators (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Recorded Investment [Line Items]
Minimum Balance For Classified Loans to be Evaluated for Impairment	$ 500,000
Recorded investment, Related allowance	200,000	2,200,000
Recorded investment with specific reserve allocation	500,000	6,100,000
Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	571,704,000	539,743,000
Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	9,807,000	8,651,000
Total Consumer Loan Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1,516,115,000	1,481,241,000
Total Consumer Loan Financing Receivable [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1,503,604,000	1,472,476,000
Total Consumer Loan Financing Receivable [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	12,236,000	8,765,000
Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1,446,436,000	1,308,483,000
Commercial Loans [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1,316,413,000	1,188,486,000
Commercial Loans [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	34,876,000	41,887,000
Commercial Loans [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	94,622,000	78,015,000
Commercial Loans [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	525,000	95,000
Commercial Loans [Member] | Commercial Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	511,074,000	467,755,000
Commercial Loans [Member] | Commercial Financing Receivable [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	470,332,000	441,834,000
Commercial Loans [Member] | Commercial Financing Receivable [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	10,346,000	4,830,000
Commercial Loans [Member] | Commercial Financing Receivable [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	29,940,000	21,091,000
Commercial Loans [Member] | Commercial Financing Receivable [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	456,000	0
Commercial Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	834,899,000	737,235,000
Commercial Loans [Member] | Commercial Real Estate [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	758,673,000	654,974,000
Commercial Loans [Member] | Commercial Real Estate [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	24,478,000	35,461,000
Commercial Loans [Member] | Commercial Real Estate [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	51,748,000	46,800,000
Commercial Loans [Member] | Commercial Real Estate [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0	0
Commercial Loans [Member] | Agricultural Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	66,537,000	67,556,000
Commercial Loans [Member] | Agricultural Financing Receivable [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	58,481,000	61,195,000
Commercial Loans [Member] | Agricultural Financing Receivable [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	42,000	660,000
Commercial Loans [Member] | Agricultural Financing Receivable [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	7,945,000	5,606,000
Commercial Loans [Member] | Agricultural Financing Receivable [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	69,000	95,000
Commercial Loans [Member] | Agricultural Real Estate Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	33,926,000	35,937,000
Commercial Loans [Member] | Agricultural Real Estate Financing Receivable [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	28,927,000	30,483,000
Commercial Loans [Member] | Agricultural Real Estate Financing Receivable [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	10,000	936,000
Commercial Loans [Member] | Agricultural Real Estate Financing Receivable [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	4,989,000	4,518,000
Commercial Loans [Member] | Agricultural Real Estate Financing Receivable [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0	0
Commercial Loans [Member] | Small Business Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	256,141,000	271,888,000
Commercial Loans [Member] | Small Business Financing Receivable [Member] | Non-classified [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	237,887,000	253,120,000
Commercial Loans [Member] | Small Business Financing Receivable [Member] | Classified [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	18,254,000	18,768,000
Commercial Loans [Member] | Total Small Business Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	256,141,000	271,888,000
Consumer Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded investment, Related allowance	175,000	2,211,000
Consumer Loans and Leases [Member] | Indirect Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	873,103,000	828,927,000
Consumer Loans and Leases [Member] | Indirect Financing Receivable [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	870,270,000	826,956,000
Consumer Loans and Leases [Member] | Indirect Financing Receivable [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2,833,000	1,971,000
Consumer Loans and Leases [Member] | Direct Financing Receivable Member [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	73,367,000	76,636,000
Consumer Loans and Leases [Member] | Direct Financing Receivable Member [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	72,849,000	76,237,000
Consumer Loans and Leases [Member] | Direct Financing Receivable Member [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	518,000	399,000
Consumer Loans and Leases [Member] | Home Equity Financing Receivables [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	569,645,000	575,678,000
Consumer Loans and Leases [Member] | Home Equity Financing Receivables [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	560,760,000	569,283,000
Consumer Loans and Leases [Member] | Home Equity Financing Receivables [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	8,885,000	6,395,000
Residential Real Estate Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	581,511,000	548,394,000
Residential Real Estate Mortgages [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	571,704,000	539,743,000
Residential Real Estate Mortgages [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	$ 9,807,000	$ 8,651,000