Loan and Lease Financings (Details)
3 Months Ended
Mar. 31, 2016
USD ($)
item
Dec. 31, 2015
USD ($)
Receivables [Abstract]    
Number of methods to assess credit risk | item 2  
Loan and Lease Financings    
Recorded investment in loans and leases $ 4,031,975,000 $ 3,994,692,000
Loan and lease financings excluding residential real estate and consumer loans    
Loan and Lease Financings    
Recorded investment in loans and leases 3,418,632,000 3,382,084,000
Commercial and agricultural    
Loan and Lease Financings    
Recorded investment in loans and leases 749,024,000 744,749,000
Auto and light truck    
Loan and Lease Financings    
Recorded investment in loans and leases 428,455,000 425,236,000
Medium and heavy duty truck    
Loan and Lease Financings    
Recorded investment in loans and leases 272,917,000 278,254,000
Aircraft financing    
Loan and Lease Financings    
Recorded investment in loans and leases 783,844,000 778,012,000
Construction equipment financing    
Loan and Lease Financings    
Recorded investment in loans and leases 467,782,000 455,565,000
Commercial real estate    
Loan and Lease Financings    
Recorded investment in loans and leases 716,610,000 700,268,000
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 3,317,782,000 3,278,484,000
Credit Quality Grades 1-6 | Commercial and agricultural    
Loan and Lease Financings    
Recorded investment in loans and leases 719,127,000 710,030,000
Credit Quality Grades 1-6 | Auto and light truck    
Loan and Lease Financings    
Recorded investment in loans and leases 414,418,000 413,836,000
Credit Quality Grades 1-6 | Medium and heavy duty truck    
Loan and Lease Financings    
Recorded investment in loans and leases 270,829,000 275,367,000
Credit Quality Grades 1-6 | Aircraft financing    
Loan and Lease Financings    
Recorded investment in loans and leases 751,761,000 750,264,000
Credit Quality Grades 1-6 | Construction equipment financing    
Loan and Lease Financings    
Recorded investment in loans and leases 463,858,000 448,683,000
Credit Quality Grades 1-6 | Commercial real estate    
Loan and Lease Financings    
Recorded investment in loans and leases 697,789,000 680,304,000
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 100,850,000 103,600,000
Credit Quality Grades 7-12 | Commercial and agricultural    
Loan and Lease Financings    
Recorded investment in loans and leases 29,897,000 34,719,000
Credit Quality Grades 7-12 | Auto and light truck    
Loan and Lease Financings    
Recorded investment in loans and leases 14,037,000 11,400,000
Credit Quality Grades 7-12 | Medium and heavy duty truck    
Loan and Lease Financings    
Recorded investment in loans and leases 2,088,000 2,887,000
Credit Quality Grades 7-12 | Aircraft financing    
Loan and Lease Financings    
Recorded investment in loans and leases 32,083,000 27,748,000
Credit Quality Grades 7-12 | Construction equipment financing    
Loan and Lease Financings    
Recorded investment in loans and leases 3,924,000 6,882,000
Credit Quality Grades 7-12 | Commercial real estate    
Loan and Lease Financings    
Recorded investment in loans and leases $ 18,821,000 $ 19,964,000