Loan and Lease Financings (Details) (USD $)	3 Months Ended
	Mar. 31, 2014 item	Dec. 31, 2013	Mar. 31, 2013
Receivables [Abstract]
Number of methods to assess credit risk	2
Loan and Lease Financings
Recorded investment in loans and leases	$ 3,577,568,000	$ 3,549,324,000	$ 3,373,218,000
Loan and lease financings excluding residential real estate and consumer loans
Loan and Lease Financings
Recorded investment in loans and leases	2,997,045,000	2,964,213,000
Commercial and agricultural loans
Loan and Lease Financings
Recorded investment in loans and leases	698,246,000	679,492,000	647,661,000
Auto and light truck
Loan and Lease Financings
Recorded investment in loans and leases	388,665,000	391,649,000	412,569,000
Medium and heavy duty truck
Loan and Lease Financings
Recorded investment in loans and leases	237,906,000	237,854,000	203,667,000
Aircraft financing
Loan and Lease Financings
Recorded investment in loans and leases	730,803,000	738,133,000	699,241,000
Construction equipment financing
Loan and Lease Financings
Recorded investment in loans and leases	352,796,000	333,088,000	285,916,000
Commercial real estate
Loan and Lease Financings
Recorded investment in loans and leases	588,629,000	583,997,000	566,355,000
Credit Quality Grades 1-6 | Loan and lease financings excluding residential real estate and consumer loans
Loan and Lease Financings
Recorded investment in loans and leases	2,891,728,000	2,855,015,000
Credit Quality Grades 1-6 | Commercial and agricultural loans
Loan and Lease Financings
Recorded investment in loans and leases	671,796,000	652,620,000
Credit Quality Grades 1-6 | Auto and light truck
Loan and Lease Financings
Recorded investment in loans and leases	379,015,000	378,392,000
Credit Quality Grades 1-6 | Medium and heavy duty truck
Loan and Lease Financings
Recorded investment in loans and leases	233,505,000	235,465,000
Credit Quality Grades 1-6 | Aircraft financing
Loan and Lease Financings
Recorded investment in loans and leases	697,505,000	704,997,000
Credit Quality Grades 1-6 | Construction equipment financing
Loan and Lease Financings
Recorded investment in loans and leases	345,542,000	325,849,000
Credit Quality Grades 1-6 | Commercial real estate
Loan and Lease Financings
Recorded investment in loans and leases	564,365,000	557,692,000
Credit Quality Grades 7-12
Loan and Lease Financings
Relationships reviewed quarterly as part of management's evaluation of the appropriateness of the reserve for loan and lease losses	100,000
Credit Quality Grades 7-12 | Loan and lease financings excluding residential real estate and consumer loans
Loan and Lease Financings
Recorded investment in loans and leases	105,317,000	109,198,000
Credit Quality Grades 7-12 | Commercial and agricultural loans
Loan and Lease Financings
Recorded investment in loans and leases	26,450,000	26,872,000
Credit Quality Grades 7-12 | Auto and light truck
Loan and Lease Financings
Recorded investment in loans and leases	9,650,000	13,257,000
Credit Quality Grades 7-12 | Medium and heavy duty truck
Loan and Lease Financings
Recorded investment in loans and leases	4,401,000	2,389,000
Credit Quality Grades 7-12 | Aircraft financing
Loan and Lease Financings
Recorded investment in loans and leases	33,298,000	33,136,000
Credit Quality Grades 7-12 | Construction equipment financing
Loan and Lease Financings
Recorded investment in loans and leases	7,254,000	7,239,000
Credit Quality Grades 7-12 | Commercial real estate
Loan and Lease Financings
Recorded investment in loans and leases	$ 24,264,000	$ 26,305,000