Loans - Schedule Of Loans By Portfolio Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2019		Sep. 30, 2019	Dec. 31, 2018		Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 31,061,111	[1]		$ 27,535,532	[1]		$ 27,658,929
Allowance for loan losses	200,307			180,424			189,555	$ 202,068
Total net loans	30,860,804			27,355,108
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	158,598			130,258
Commercial | Commercial, financial, and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	20,051,091			16,514,328			16,057,273
Allowance for loan losses	122,486			98,947			98,211	89,398
Commercial | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	4,337,017			4,030,870			4,214,695
Allowance for loan losses	36,112			31,311			28,427	33,852
Consumer | Consumer real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	6,006,749			6,249,516			6,479,242
Allowance for loan losses	19,624			26,439			39,823	51,424
Consumer | Permanent mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	170,390			222,448			287,820
Allowance for loan losses	8,819			11,000			13,113	15,222
Consumer | Credit card & other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	495,864			518,370			619,899
Allowance for loan losses	$ 13,266			12,727			$ 9,981	$ 12,172
Consumer | Restricted And Secured Consumer Real Estate Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income				$ 16,200
Restatement Adjustment | Commercial | Commercial, financial, and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income			$ (410,000)			$ (410,000)

[1] December 31, 2019 and 2018 include $18.8 million and $28.6 million, respectively, of held-to-maturity consumer mortgage loans secured by residential real estate in process of foreclosure.