Loan and Lease Financings (Details 3) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	$ 3,539,708	$ 3,494,275
30-59 Days Past Due	9,006	13,907
60-89 Days Past Due	3,867	4,154
90 Days or More Past Due and Accruing	307	281
Total Accruing Loans	3,552,888	3,512,617
Nonaccrual	24,680	36,707
Total loans and leases	3,577,568	3,549,324	3,373,218
Commercial and agricultural loans
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	686,536	667,462
30-59 Days Past Due	200	263
60-89 Days Past Due	1	2
Total Accruing Loans	686,737	667,727
Nonaccrual	11,509	11,765
Total loans and leases	698,246	679,492	647,661
Auto and light truck
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	388,074	387,881
30-59 Days Past Due	241	222
60-89 Days Past Due	2	36
Total Accruing Loans	388,317	388,139
Nonaccrual	348	3,510
Total loans and leases	388,665	391,649	412,569
Medium and heavy duty truck
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	237,762	237,645
30-59 Days Past Due	12	20
60-89 Days Past Due	0	0
Total Accruing Loans	237,774	237,665
Nonaccrual	132	189
Total loans and leases	237,906	237,854	203,667
Aircraft financing
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	716,622	713,832
30-59 Days Past Due	7,072	10,309
60-89 Days Past Due	3,528	3,627
Total Accruing Loans	727,222	727,768
Nonaccrual	3,581	10,365
Total loans and leases	730,803	738,133	699,241
Construction equipment financing
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	351,206	331,083
30-59 Days Past Due	424	973
60-89 Days Past Due	0	0
Total Accruing Loans	351,630	332,056
Nonaccrual	1,166	1,032
Total loans and leases	352,796	333,088	285,916
Commercial real estate
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	583,474	576,933
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
Total Accruing Loans	583,474	576,933
Nonaccrual	5,155	7,064
Total loans and leases	588,629	583,997	566,355
Residential real estate
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	452,365	456,782
30-59 Days Past Due	459	1,334
60-89 Days Past Due	201	269
90 Days or More Past Due and Accruing	274	197
Total Accruing Loans	453,299	458,582
Nonaccrual	2,379	2,399
Total loans and leases	455,678	460,981	445,160
Consumer loans
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	123,669	122,657
30-59 Days Past Due	598	786
60-89 Days Past Due	135	220
90 Days or More Past Due and Accruing	33	84
Total Accruing Loans	124,435	123,747
Nonaccrual	410	383
Total loans and leases	$ 124,845	$ 124,130	$ 112,649