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	Dec. 31, 2023	Dec. 31, 2022
Aggregate  Fair Value
Loans measured at fair value	$ 450	$ 723
Past due loans of 30-89 days	1	1
Nonaccrual loans	2	2
Aggregate Unpaid Principal Balance
Loans measured at fair value	456	733
Past due loans of 30-89 days	1	1
Nonaccrual loans	2	2
Difference
Loans measured at fair value	(6)	(10)
Past due loans of 30-89 days	0	0
Nonaccrual loans	$ 0	$ 0