Allowance for Credit Losses and Credit Quality - Rollfowards of the Allowance for Loan and Lease Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Allowance for loan and lease losses [Roll Forward]
Balance, beginning of period	$ 406,383	$ 147,972	$ 113,052	$ 157,446
Charge-offs	(9,958)	(21,066)	(24,687)	(45,497)
Recoveries	6,563	6,984	15,815	12,761
Net (charge-offs) recoveries	(3,395)	(14,082)	(8,872)	(32,736)
Provision for credit losses	58,126	13,569	151,116	23,691
Other		(956)	(174)	(1,898)
Balance, end of period	461,114	146,503	461,114	146,503
Unfunded commitments [Roll Forward]
Balance, beginning of period	22,188	1,941	3,528	1,428
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Net (charge-offs) recoveries	0	0	0	0
Provision for credit losses	20,600	(5)	24,553	508
Other		0	0	0
Balance, end of period	42,788	1,936	42,788	1,936
Allowance for loan, leases and unfunded commitments [Roll Forward]
Balance, beginning of period	428,571	149,913	116,580	158,874
Charge-offs	(9,958)	(21,066)	(24,687)	(45,497)
Recoveries	6,563	6,984	15,815	12,761
Net (charge-offs) recoveries	(3,395)	(14,082)	(8,872)	(32,736)
Provision for credit losses	78,726	13,564	175,669	24,199
Other		(956)	(174)	(1,898)
Balance, end of period	503,902	148,439	503,902	148,439
Consumer
Allowance for loan and lease losses [Roll Forward]
Balance, beginning of period	175,057	74,297	28,572	80,017
Charge-offs	(4,997)	(12,958)	(10,845)	(29,824)
Recoveries	3,629	5,653	8,337	10,510
Net (charge-offs) recoveries	(1,368)	(7,305)	(2,508)	(19,314)
Provision for credit losses	(16,004)	4,693	24,284	11,951
Other		(974)	0	(1,943)
Balance, end of period	157,685	70,711	157,685	70,711
Commercial
Allowance for loan and lease losses [Roll Forward]
Balance, beginning of period	231,326	73,675	84,480	77,429
Charge-offs	(4,961)	(8,108)	(13,842)	(15,673)
Recoveries	2,934	1,331	7,478	2,251
Net (charge-offs) recoveries	(2,027)	(6,777)	(6,364)	(13,422)
Provision for credit losses	74,130	8,876	126,832	11,740
Other		18	(174)	45
Balance, end of period	$ 303,429	$ 75,792	303,429	$ 75,792
Cumulative Effect, Period of Adoption, Adjustment
Allowance for loan and lease losses [Roll Forward]
Balance, beginning of period			205,992
Unfunded commitments [Roll Forward]
Balance, beginning of period			14,707
Allowance for loan, leases and unfunded commitments [Roll Forward]
Balance, beginning of period			220,699
Cumulative Effect, Period of Adoption, Adjustment | Consumer
Allowance for loan and lease losses [Roll Forward]
Balance, beginning of period			107,337
Cumulative Effect, Period of Adoption, Adjustment | Commercial
Allowance for loan and lease losses [Roll Forward]
Balance, beginning of period			98,655
Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for loan and lease losses [Roll Forward]
Balance, beginning of period			319,044
Unfunded commitments [Roll Forward]
Balance, beginning of period			18,235
Allowance for loan, leases and unfunded commitments [Roll Forward]
Balance, beginning of period			337,279
Cumulative Effect, Period of Adoption, Adjusted Balance | Consumer
Allowance for loan and lease losses [Roll Forward]
Balance, beginning of period			135,909
Cumulative Effect, Period of Adoption, Adjusted Balance | Commercial
Allowance for loan and lease losses [Roll Forward]
Balance, beginning of period			$ 183,135