Loan and Lease Financings (Details 3) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	$ 3,427,929	$ 3,285,951
30-59 Days Past Due	3,051	3,544
60-89 Days Past Due	5,568	1,199
90 Days or More Past Due and Accruing	245	442
Total Accruing Loans	3,436,793	3,291,136
Nonaccrual	31,325	36,417
Total loans and leases	3,468,118	3,327,553	3,268,413
Commercial and agricultural loans
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	643,495	629,035
30-59 Days Past Due	714	807
60-89 Days Past Due	750	48
Total Accruing Loans	644,959	629,890
Nonaccrual	7,221	9,179
Total loans and leases	652,180	639,069	584,996
Auto, light truck and environmental equipment
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	451,659	437,087
30-59 Days Past Due	349	202
60-89 Days Past Due	110
Total Accruing Loans	452,118	437,289
Nonaccrual	287	858
Total loans and leases	452,405	438,147	456,665
Medium and heavy duty truck
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	192,380	171,950
Total Accruing Loans	192,380	171,950
Nonaccrual	594	52
Total loans and leases	192,974	172,002	167,709
Aircraft financing
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	688,856	691,187
60-89 Days Past Due	3,725
Total Accruing Loans	692,581	691,187
Nonaccrual	11,491	5,292
Total loans and leases	704,072	696,479	685,800
Construction equipment financing
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	313,532	272,817
30-59 Days Past Due	515	598
60-89 Days Past Due		274
Total Accruing Loans	314,047	273,689
Nonaccrual	1,299	5,285
Total loans and leases	315,346	278,974	276,270
Commercial real estate
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	566,742	541,811
30-59 Days Past Due		102
60-89 Days Past Due	51
Total Accruing Loans	566,793	541,913
Nonaccrual	7,486	13,055
Total loans and leases	574,279	554,968	548,921
Residential real estate
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	451,005	434,434
30-59 Days Past Due	956	1,019
60-89 Days Past Due	600	509
90 Days or More Past Due and Accruing	220	356
Total Accruing Loans	452,781	436,318
Nonaccrual	2,546	2,323
Total loans and leases	455,327	438,641	436,909
Consumer loans
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	120,260	107,630
30-59 Days Past Due	517	816
60-89 Days Past Due	332	368
90 Days or More Past Due and Accruing	25	86
Total Accruing Loans	121,134	108,900
Nonaccrual	401	373
Total loans and leases	$ 121,535	$ 109,273	$ 111,143