New Authoritative Accounting Guidance (Details) - USD ($) $ in Thousands		3 Months Ended
	Jan. 01, 2020	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Forecast period		2 years
Historical loss experience period		1 year
Allowance for loan losses		$ 283,342	$ 161,759	$ 154,381	$ 151,859
Allowance for unfunded credit commitments		10,019	2,845
Allowance for credit losses		1,552	0
Stockholders' equity		(4,420,998)	(4,384,188)	(3,444,879)	(3,350,454)
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity		$ (452,424)	(443,559)	$ (375,983)	$ (299,642)
Cumulative Effect, Period Of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses	$ 100,400
Allowance for loan losses	92,500		92,531
Allowance for unfunded credit commitments	7,100
Allowance for credit losses	793		$ 793
PCD loans related reserves	61,600
Non-credit discount	97,700
Cumulative Effect, Period Of Adoption, Adjustment | Non-PCD Loans
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for loan losses	38,800
Cumulative Effect, Period Of Adoption, Adjustment | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity	$ 28,200