Securitizations and Variable Interest Entities - Schedule of Cost and Fair Value of Securities (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Fair Value	$ 312	$ 131
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Amortized Cost	304	124
Fair Value	312	131
Rated notes | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Amortized Cost	228	96
Fair Value	229	98
Certificates and other assets | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Amortized Cost	76	28
Fair Value	$ 83	$ 33