Loans and Leases (Allowance for credit losses on financing receivables) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Ending Balance Under ASC 310-10-35	$ 3,266	$ 6,717
Ending Balance Under ASC 450-20	35,307	34,968
Total	38,573	41,685	37,528	38,715
Ending Balance Evaluated for Impairment Under ASC 310-10-35	58,424	71,961
Ending Balance Evaluated for Impairment Under ASC 450-20	3,522,689	3,428,148
Total	3,581,113	3,500,109
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Ending Balance Under ASC 310-10-35	603	2,817
Ending Balance Under ASC 450-20	11,030	10,282
Total	11,633	13,099	9,299	11,388
Ending Balance Evaluated for Impairment Under ASC 310-10-35	8,172	14,644
Ending Balance Evaluated for Impairment Under ASC 450-20	978,541	935,553
Total	986,713	950,197
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Ending Balance Under ASC 310-10-35	365	818
Ending Balance Under ASC 450-20	12,645	13,334
Total	13,010	14,152	15,190	14,473
Ending Balance Evaluated for Impairment Under ASC 310-10-35	27,403	28,299
Ending Balance Evaluated for Impairment Under ASC 450-20	1,533,509	1,501,384
Total	1,560,912	1,529,683
Agricultural and Agricultural Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Ending Balance Under ASC 310-10-35	15	756
Ending Balance Under ASC 450-20	2,556	2,236
Total	2,571	2,992	2,195	2,138
Ending Balance Evaluated for Impairment Under ASC 310-10-35	9,006	16,667
Ending Balance Evaluated for Impairment Under ASC 450-20	361,342	360,068
Total	370,348	376,735
Residential Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Ending Balance Under ASC 310-10-35	538	605
Ending Balance Under ASC 450-20	3,133	3,115
Total	3,671	3,720	3,266	3,543
Ending Balance Evaluated for Impairment Under ASC 310-10-35	7,668	7,214
Ending Balance Evaluated for Impairment Under ASC 450-20	357,494	342,135
Total	365,162	349,349
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Ending Balance Under ASC 310-10-35	1,745	1,721
Ending Balance Under ASC 450-20	5,631	6,001
Total	7,376	7,722	7,578	7,173
Ending Balance Evaluated for Impairment Under ASC 310-10-35	6,175	5,137
Ending Balance Evaluated for Impairment Under ASC 450-20	291,803	289,008
Total	297,978	294,145
Unallocated
Financing Receivable, Allowance for Credit Losses [Line Items]
Ending Balance Under ASC 310-10-35	0	0
Ending Balance Under ASC 450-20	312	0
Total	312	0	0	0
Ending Balance Evaluated for Impairment Under ASC 310-10-35	0	0
Ending Balance Evaluated for Impairment Under ASC 450-20	0	0
Total	$ 0	$ 0