Accounting Policies and Basis of Presentation Accounting Policies and Basis of Presentation (Recently Adopted Accounting Standards) (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) loan $ / shares shares	Mar. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares	Dec. 31, 2019 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stock issued (in shares) | shares		339,958,000
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.01		$ 0.01
Stock repurchased during period (in shares) | shares		349,390
Stock repurchased during period		$ 159,700
Stock repurchased during period (in USD per share) | $ / shares		$ 457.10
Forecast period (years)	2 years
Retained earnings	$ 4,005,318		$ 3,867,252
Allowance for credit loss	210,651	$ 209,259	224,314	$ 225,141
Commercial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss	74,864	72,410	80,842	$ 142,369
Loans and leases, not acquired in a transfer accounted for as debt securities	$ 23,097,302		22,558,060
SBA-PPP
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of loans originated | loan	9,600
Loans receivable, period increase	$ 1,100,000
Loans and leases, not acquired in a transfer accounted for as debt securities	2,800,000
SBA-PPP | Commercial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	$ 2,769,906		$ 2,406,291
Class A Common Stock
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stock repurchased during period		$ 159,704
Class A Common Stock | Repurchases From Ella Ann Holding
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stock repurchased during period (in shares) | shares	45,000