Allowance for Loan Losses - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2020		Jun. 30, 2019	Jun. 30, 2020		Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019		Mar. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 32,708,937	[1]	$ 29,712,810	$ 32,708,937	[1]	$ 29,712,810		$ 31,061,111	[1]
Allowance for loan losses	537,881		192,749	$ 537,881		192,749	$ 444,490	200,307		$ 184,911	$ 180,424
Forecast period to estimate expected credit losses				4 years
Term to estimate expected credit losses determined by macroeconomics variable				3 years
Additional term to estimated expected credit losses determined by microeconomics variable diminishing				1 year
Measurement period of historical losses, pro rata period				1 year
Expense/(Credit) on unfunded commitments	11,158		(489)	$ 20,388		(93)
Consumer real estate | C&I
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted average life				3 years
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses								158,598
Commercial | C&I
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	21,393,893		19,054,269	$ 21,393,893		19,054,269		20,051,091
Allowance for loan losses	318,722		$ 116,096	$ 318,722		$ 116,096	$ 254,516	122,486		$ 103,713	$ 98,947
HELOC and R/E Installment Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted average life				5 years
General C&I
Accounts, Notes, Loans and Financing Receivable [Line Items]
Collateral for secured borrowings	65,000			$ 65,000
Collateral, charge off	1,500			13,000
General C&I | Commercial | C&I
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	17,164,125			17,164,125				$ 15,395,996
HELOC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Collateral for secured borrowings	10,000			10,000
R/E Installment Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Collateral for secured borrowings	26,000			26,000
COVID-19 Deferrals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	860			860
Paycheck Protection Plan | Commercial | C&I
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 2,100,000			$ 2,100,000

[1] June 30, 2020 and December 31, 2019 include $16.9 million and $18.8 million, respectively, of held-to-maturity consumer mortgage loans secured by residential real estate in process of foreclosure.