Loan and Lease Financings (Details 4) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	$ 4,481,921	$ 4,158,757
90 Days or More Past Due and Accruing	459	416
Total Accruing Loans	4,508,273	4,168,164
Nonaccrual	19,405	19,907
Total loans and leases	4,527,678	4,188,071
Increase in interest income	1,140	1,110	$ 1,030
Commercial and agricultural
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	927,113	808,283
Total Accruing Loans	927,394	808,283
Nonaccrual	2,603	3,981
Total loans and leases	929,997	812,264
Auto and light truck
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	485,885	411,300
Total Accruing Loans	488,775	411,598
Nonaccrual	8,041	166
Total loans and leases	496,816	411,764
Medium and heavy duty truck
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	296,564	294,790
Total Accruing Loans	296,564	294,790
Nonaccrual	371	0
Total loans and leases	296,935	294,790
Aircraft
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	823,638	791,559
Total Accruing Loans	842,700	796,304
Nonaccrual	1,957	6,110
Total loans and leases	844,657	802,414
Construction equipment
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	561,665	493,131
Total Accruing Loans	562,446	494,677
Nonaccrual	991	1,248
Total loans and leases	563,437	495,925
Commercial real estate
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	738,006	713,482
Total Accruing Loans	738,150	713,615
Nonaccrual	3,418	5,555
Total loans and leases	741,568	719,170
Residential real estate and home equity
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	521,943	517,212
90 Days or More Past Due and Accruing	429	394
Total Accruing Loans	524,232	519,290
Nonaccrual	1,890	2,641
Total loans and leases	526,122	521,931
Consumer
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Current	127,107	129,000
90 Days or More Past Due and Accruing	30	22
Total Accruing Loans	128,012	129,607
Nonaccrual	134	206
Total loans and leases	128,146	129,813
30 to 59 Days Past Due
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	20,360	5,169
30 to 59 Days Past Due | Commercial and agricultural
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	281	0
30 to 59 Days Past Due | Auto and light truck
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	2,869	298
30 to 59 Days Past Due | Medium and heavy duty truck
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	0	0
30 to 59 Days Past Due | Aircraft
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	14,570	1,429
30 to 59 Days Past Due | Construction equipment
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	333	1,546
30 to 59 Days Past Due | Commercial real estate
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	23	133
30 to 59 Days Past Due | Residential real estate and home equity
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	1,508	1,310
30 to 59 Days Past Due | Consumer
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	776	453
60 to 89 Days Past Due
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	5,533	3,822
60 to 89 Days Past Due | Commercial and agricultural
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	0	0
60 to 89 Days Past Due | Auto and light truck
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	21	0
60 to 89 Days Past Due | Medium and heavy duty truck
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	0	0
60 to 89 Days Past Due | Aircraft
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	4,492	3,316
60 to 89 Days Past Due | Construction equipment
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	448	0
60 to 89 Days Past Due | Commercial real estate
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	121	0
60 to 89 Days Past Due | Residential real estate and home equity
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	352	374
60 to 89 Days Past Due | Consumer
Recorded investment of loans and leases, segregated by class, with delinquency aging and nonaccrual status
Past Due	$ 99	$ 132