Allowance for Loan Losses - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020		Mar. 31, 2019	Dec. 31, 2019	[1]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 33,378,303	[1]	$ 27,990,048	$ 31,061,111
Expense/(Credit) on unfunded commitments	$ 9,230		$ 396
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
Consumer real estate | C&I
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted average life	3 years
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	$ 32,000
Collateral, charge off	6,000
HELOC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Collateral for secured borrowings	10,000
R/E Installment Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Collateral for secured borrowings	$ 23,000

[1] March 31, 2020 and December 31, 2019 include $20.8 million and $18.8 million, respectively, of held-to-maturity consumer mortgage loans secured by residential real estate in process of foreclosure.