Financial Information - ASU 2016-13 (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans, net of unearned income	$ 59,706,531			$ 31,061,111
Allowance for loan and lease losses	988,102	$ 537,881		200,307	$ 193,149	$ 192,749	$ 180,424
Other assets	4,135,056			2,297,405
Other liabilities	1,695,868			990,094
Retained earnings	2,110,990			1,798,442
Total liabilities and equity	$ 83,029,579			$ 43,310,900
Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans, net of unearned income			$ 2,980
Allowance for loan and lease losses			(106,394)
Other assets (deferred taxes)			31,330
Other assets			(72,084)
Other liabilities			23,973
Retained earnings			(96,057)
Total liabilities and equity			$ (72,084)