Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Recorded Investment in Loans Modified in TDRs within Previous 12 months Subsequently Defaulted (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded investment in loans modified in TDRs	$ 0	$ 10	$ 0	$ 10
Cash flow dependent
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded investment in loans modified in TDRs	0	10	0	10
Cash flow dependent | Sponsor led buyout
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded investment in loans modified in TDRs	$ 0	$ 10	$ 0	$ 10