Fair Value Measures - Differences Between Aggregate Fair Value and Aggregate Remaining Contractual Principal Balance Outstanding - Fair Value Option (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Fair Value, Option, Quantitative Disclosures
Unpaid Principal Balance	$ 926	$ 1,095
Fair Value	945	1,115
Fair Value Over / (Under) UPB	19	20
Total other performing loans
Fair Value, Option, Quantitative Disclosures
Unpaid Principal Balance	926	1,095
Fair Value	945	1,115
Fair Value Over / (Under) UPB	19	20
Loans held-for-sale
Fair Value, Option, Quantitative Disclosures
Unpaid Principal Balance	926	1,095
Fair Value	945	1,115
Fair Value Over / (Under) UPB	19	20
Loans held-for-sale | Total other performing loans
Fair Value, Option, Quantitative Disclosures
Unpaid Principal Balance	926	1,095
Fair Value	945	1,115
Fair Value Over / (Under) UPB	$ 19	$ 20