Allowance for Loan and Lease Losses and Credit Quality Information - Allowance for Loan and Lease Losses and Balances Outstanding by Allowance Methodology (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for loan and lease losses:
Collectively evaluated for impairment		$ 125,253	$ 147,105
Individually evaluated for impairment		32,193	23,936
Total		157,446	171,041	$ 160,269	$ 156,054
Loans and leases outstanding:
Collectively evaluated for impairment		18,872,416	18,869,356
Individually evaluated for impairment		196,078	223,260
Loans acquired with deteriorated credit quality		3,817	11,844	17
Total loans and leases	[1]	19,072,311	19,104,460
Consumer Real Estate
Allowance for loan and lease losses:
Collectively evaluated for impairment		22,134	28,851
Individually evaluated for impairment		22,732	18,317
Total		44,866	47,168	59,448	67,992
Loans and leases outstanding:
Collectively evaluated for impairment		5,295,817	4,675,626
Individually evaluated for impairment		114,523	144,070
Loans acquired with deteriorated credit quality		0	0
Total loans and leases		5,410,340	4,819,696
Commercial
Allowance for loan and lease losses:
Collectively evaluated for impairment		36,411	35,635
Individually evaluated for impairment		4,771	1,560
Total		41,182	37,195	32,695	30,185
Loans and leases outstanding:
Collectively evaluated for impairment		3,815,422	3,524,864
Individually evaluated for impairment		35,881	36,329
Loans acquired with deteriorated credit quality		0	0
Total loans and leases		3,851,303	3,561,193
Leasing and Equipment Finance
Allowance for loan and lease losses:
Collectively evaluated for impairment		20,108	19,083
Individually evaluated for impairment		3,683	3,445
Total		23,791	22,528	21,350	19,018
Loans and leases outstanding:
Collectively evaluated for impairment		4,672,168	4,721,905
Individually evaluated for impairment		23,755	27,912
Loans acquired with deteriorated credit quality		3,817	11,844
Total loans and leases		4,699,740	4,761,661
Inventory Finance
Allowance for loan and lease losses:
Collectively evaluated for impairment		11,621	12,945
Individually evaluated for impairment		835	288
Total		12,456	13,233	13,932	11,128
Loans and leases outstanding:
Collectively evaluated for impairment		3,099,073	2,735,638
Individually evaluated for impairment		8,283	4,116
Loans acquired with deteriorated credit quality		0	0
Total loans and leases		3,107,356	2,739,754
Auto Finance
Allowance for loan and lease losses:
Collectively evaluated for impairment		34,157	49,900
Individually evaluated for impairment		172	325
Total		34,329	50,225	32,310	26,486
Loans and leases outstanding:
Collectively evaluated for impairment		1,968,645	3,188,810
Individually evaluated for impairment		13,632	10,829
Loans acquired with deteriorated credit quality		0	0
Total loans and leases		1,982,277	3,199,639
Other
Allowance for loan and lease losses:
Collectively evaluated for impairment		822	691
Individually evaluated for impairment		0	1
Total		822	692	$ 534	$ 1,245
Loans and leases outstanding:
Collectively evaluated for impairment		21,291	22,513
Individually evaluated for impairment		4	4
Loans acquired with deteriorated credit quality		0	0
Total loans and leases		$ 21,295	$ 22,517

[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.