Revenue from Contracts with Customers - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) line_of_business	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of lines of business	2	2
Accrued Interest and Fees Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables related to contracts with customers	$ 2,680	$ 2,680	$ 2,770