Loans (Aging of Recorded Investment in Past Due Loans by Class of Loans) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Ending Loans Balance (1)	$ 1,201,598	[1]	$ 1,213,423	[2]
30-59 Days Past Due	5,582	[1]	4,508	[2]
60-89 Days Past Due	639	[1]	713	[2]
90 Days or More Past Due	3,129	[1]	2,964	[2]
Total Past Due	9,350	[1]	8,185	[2]
Loans Not Past Due	1,192,248	[1]	1,205,238	[2]
Commercial and Industrial Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Ending Loans Balance (1)	332,987	[1]	336,307	[2]
30-59 Days Past Due	285		436
60-89 Days Past Due	356		133
90 Days or More Past Due	566		448
Total Past Due	1,207		1,017
Loans Not Past Due	331,780		335,290
Commercial Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Ending Loans Balance (1)	499,717	[1]	489,796	[2]
30-59 Days Past Due	560		1,352
60-89 Days Past Due	23		0
90 Days or More Past Due	2,364		2,063
Total Past Due	2,947		3,415
Loans Not Past Due	496,770		486,381
Agricultural Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Ending Loans Balance (1)	167,285	[1]	182,575	[2]
30-59 Days Past Due	2,415		42
60-89 Days Past Due	0		14
90 Days or More Past Due	0		0
Total Past Due	2,415		56
Loans Not Past Due	164,870		182,519
Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Ending Loans Balance (1)	73,175	[1]	74,699	[2]
30-59 Days Past Due	364		177
60-89 Days Past Due	232		48
90 Days or More Past Due	73		178
Total Past Due	669		403
Loans Not Past Due	72,506		74,296
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Ending Loans Balance (1)	41,891	[1]	41,231	[2]
30-59 Days Past Due	184		431
60-89 Days Past Due	28		23
90 Days or More Past Due	9		18
Total Past Due	221		472
Loans Not Past Due	41,670		40,759
Residential Mortgage Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Ending Loans Balance (1)	86,543	[1]	88,815	[2]
30-59 Days Past Due	1,774		2,070
60-89 Days Past Due	0		495
90 Days or More Past Due	117		257
Total Past Due	1,891		2,822
Loans Not Past Due	84,652		85,993
Loans Acquired With Deteriorated Credit Quality [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Ending Loans Balance (1)	10,477		11,174
30-59 Days Past Due	0		0
60-89 Days Past Due	0		120
90 Days or More Past Due	118		0
Total Past Due	118		120
Loans Not Past Due	$ 10,359		$ 11,054

[1] Total recorded investment in loans includes $4,980 in accrued interest

[2] Total recorded investment in loans includes $5,522 in accrued interest