Loans and Leases (Loans and Leases Not Covered by Share Agreements (Past Due Financing Receivables)) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	$ 7,173	$ 4,036
60-89 Days Past Due	2,056	1,127
90 Days or More Past Due	0	0
Total Past Due	9,229	5,163
Current	2,772,785	2,424,812
Nonaccrual	43,156	57,435
Total	2,825,170	2,487,410
Commercial Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	2,774	888
60-89 Days Past Due	1,019	479
90 Days or More Past Due	0	0
Total Past Due	3,793	1,367
Current	1,967,406	1,760,547
Nonaccrual	30,128	47,536
Total	2,001,327	1,809,450
Agricultural Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	687	32
60-89 Days Past Due	0	0
90 Days or More Past Due	0	0
Total Past Due	687	32
Current	324,545	262,409
Nonaccrual	3,079	534
Total	328,311	262,975
Residential Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,278	940
60-89 Days Past Due	234	93
90 Days or More Past Due	0	0
Total Past Due	1,512	1,033
Current	241,860	188,865
Nonaccrual	6,317	4,538
Total	249,689	194,436
Consumer Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	2,434	2,176
60-89 Days Past Due	803	555
90 Days or More Past Due	0	0
Total Past Due	3,237	2,731
Current	238,809	212,541
Nonaccrual	3,632	4,827
Total	245,678	220,099
Finance Leases Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
90 Days or More Past Due	0	0
Total Past Due	0	0
Current	165	450
Nonaccrual	0	0
Total	165	450
Commercial | Commercial Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,143	220
60-89 Days Past Due	525	479
90 Days or More Past Due	0	0
Total Past Due	1,668	699
Current	708,294	643,273
Nonaccrual	2,181	1,694
Total	712,143	645,666
Commercial Real Estate | Commercial Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,631	668
60-89 Days Past Due	494	0
90 Days or More Past Due	0	0
Total Past Due	2,125	668
Current	1,259,112	1,117,274
Nonaccrual	27,947	45,842
Total	$ 1,289,184	$ 1,163,784