Financial Information - ASU 2016-02 (Details) - USD ($) $ in Thousands	Sep. 30, 2019		Jan. 01, 2019	Dec. 31, 2018		Sep. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans, net of unearned income	$ 31,260,833	[1]		$ 27,535,532	[1]	$ 27,350,214
Premises and equipment, net	451,600			494,041
Other assets	1,912,685			1,802,939
Other liabilities	763,534			580,335
Undivided profits	$ 1,725,846			$ 1,542,408
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans, net of unearned income			$ 3,450
Premises and equipment, net			2,718
Other assets			183,884
Other liabilities			(191,010)
Undivided profits			$ 1,011

[1] September 30, 2019 and December 31, 2018 include $18.2 million and $28.6 million, respectively, of held-to-maturity consumer mortgage loans secured by residential real estate in process of foreclosure.