Loans and Leases - Purchased Credit Impaired Loans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	$ 503	$ 45	$ 8
Financial Asset Acquired with Credit Deterioration
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance - purchased credit-impaired loans		2
Allowance for loan and lease losses write-offs		6	7
Provision for credit losses		$ 1	$ 1