Allowance for Loan and Lease Losses and Credit Quality Information - Accruing and Non-accrual Loans and Leases (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Accruing and Non-accrual Loans and Leases
Current-59 days Delinquent and Accruing		$ 18,937,811	$ 18,962,699
60 to 89 Days Delinquent and Accruing		21,138	16,247
90 Days or More Delinquent and Accruing		7,444	6,932
Total accruing		18,966,393	18,985,878
Non-accrual		105,918	118,582
Total loans and leases	[1]	19,072,311	19,104,460
Portfolios acquired with deteriorated credit quality
Accruing and Non-accrual Loans and Leases
Current-59 days Delinquent and Accruing		3,639	10,283
60 to 89 Days Delinquent and Accruing		0	361
90 Days or More Delinquent and Accruing		178	1,200
Total accruing		3,817	11,844
Non-accrual		0	0
Total loans and leases		3,817	11,844
Consumer real estate
Accruing and Non-accrual Loans and Leases
Current-59 days Delinquent and Accruing		5,345,805	4,730,538
60 to 89 Days Delinquent and Accruing		4,494	5,341
90 Days or More Delinquent and Accruing		1,276	593
Total accruing		5,351,575	4,736,472
Non-accrual		58,765	83,224
Total loans and leases		5,410,340	4,819,696
Consumer real estate | First mortgage lien
Accruing and Non-accrual Loans and Leases
Current-59 days Delinquent and Accruing		2,403,391	1,892,771
60 to 89 Days Delinquent and Accruing		3,281	4,073
90 Days or More Delinquent and Accruing		1,276	593
Total accruing		2,407,948	1,897,437
Non-accrual		36,432	61,950
Total loans and leases		2,444,380	1,959,387
Consumer real estate | Junior lien
Accruing and Non-accrual Loans and Leases
Current-59 days Delinquent and Accruing		2,942,414	2,837,767
60 to 89 Days Delinquent and Accruing		1,213	1,268
90 Days or More Delinquent and Accruing		0	0
Total accruing		2,943,627	2,839,035
Non-accrual		22,333	21,274
Total loans and leases		2,965,960	2,860,309
Commercial
Accruing and Non-accrual Loans and Leases
Current-59 days Delinquent and Accruing		3,836,277	3,554,407
60 to 89 Days Delinquent and Accruing		1	1
90 Days or More Delinquent and Accruing		0	0
Total accruing		3,836,278	3,554,408
Non-accrual		15,025	6,785
Total loans and leases		3,851,303	3,561,193
Commercial | Commercial real estate
Accruing and Non-accrual Loans and Leases
Current-59 days Delinquent and Accruing		2,903,629	2,744,500
60 to 89 Days Delinquent and Accruing		0	0
90 Days or More Delinquent and Accruing		0	0
Total accruing		2,903,629	2,744,500
Non-accrual		4,518	6,785
Total loans and leases		2,908,147	2,751,285
Commercial | Commercial business
Accruing and Non-accrual Loans and Leases
Current-59 days Delinquent and Accruing		932,648	809,907
60 to 89 Days Delinquent and Accruing		1	1
90 Days or More Delinquent and Accruing		0	0
Total accruing		932,649	809,908
Non-accrual		10,507	0
Total loans and leases		943,156	809,908
Leasing and equipment finance
Accruing and Non-accrual Loans and Leases
Current-59 days Delinquent and Accruing		4,670,021	4,726,339
60 to 89 Days Delinquent and Accruing		7,996	4,272
90 Days or More Delinquent and Accruing		2,642	2,117
Total accruing		4,680,659	4,732,728
Non-accrual		15,264	17,089
Total loans and leases		4,695,923	4,749,817
Inventory finance
Accruing and Non-accrual Loans and Leases
Current-59 days Delinquent and Accruing		3,098,763	2,735,430
60 to 89 Days Delinquent and Accruing		310	191
90 Days or More Delinquent and Accruing		0	17
Total accruing		3,099,073	2,735,638
Non-accrual		8,283	4,116
Total loans and leases		3,107,356	2,739,754
Auto finance
Accruing and Non-accrual Loans and Leases
Current-59 days Delinquent and Accruing		1,962,042	3,183,196
60 to 89 Days Delinquent and Accruing		8,326	6,078
90 Days or More Delinquent and Accruing		3,331	2,999
Total accruing		1,973,699	3,192,273
Non-accrual		8,578	7,366
Total loans and leases		1,982,277	3,199,639
Other
Accruing and Non-accrual Loans and Leases
Current-59 days Delinquent and Accruing		21,264	22,506
60 to 89 Days Delinquent and Accruing		11	3
90 Days or More Delinquent and Accruing		17	6
Total accruing		21,292	22,515
Non-accrual		3	2
Total loans and leases		21,295	22,517
Total loans and leases excluding portfolios acquired with deteriorated credit quality
Accruing and Non-accrual Loans and Leases
Current-59 days Delinquent and Accruing		18,934,172	18,952,416
60 to 89 Days Delinquent and Accruing		21,138	15,886
90 Days or More Delinquent and Accruing		7,266	5,732
Total accruing		18,962,576	18,974,034
Non-accrual		105,918	118,582
Total loans and leases		$ 19,068,494	$ 19,092,616

[1] (1)Loans and leases are reported at historical cost including net direct fees and costs associated with originating and acquiring loans and leases, lease residuals, unearned income and unamortized purchase premiums and discounts. The aggregate amount of these loan and lease adjustments was $(2.2) million and $33.3 million at December 31, 2018 and 2017, respectively.