Fair Value Measurements - Difference Between the Aggregate Fair Value and the Aggregate Unpaid Principal Balance for Residential Mortgage Loans Measured at Fair Value (Details) - Residential mortgage loans - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Aggregate Fair Value
Loans measured at fair value	$ 610	$ 723
Past due loans of 30-89 days		1
Non accrual loans	2	2
Aggregate Unpaid Principal Balance
Loans measured at fair value	634	733
Past due loans of 30-89 days		1
Non accrual loans	2	2
Difference
Loans measured at fair value	(24)	(10)
Past due loans of 30-89 days		0
Non accrual loans	$ 0	$ 0