Investments in Securities - Available-for-sale Securities 1 (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	$ 527	$ 584
Allowance for Credit Losses	(2)	(2)
Gross Unrealized Gains in AOCI	11	11
Gross Unrealized Losses in AOCI	(29)	(29)
Total Fair Value	507	564
Agency securities
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	384	405
Allowance for Credit Losses	0	0
Gross Unrealized Gains in AOCI	1	1
Gross Unrealized Losses in AOCI	(29)	(29)
Total Fair Value	356	377
Other mortgage-related securities
Debt Securities, Available-for-sale [Line Items]
Total Amortized Cost	143	179
Allowance for Credit Losses	(2)	(2)
Gross Unrealized Gains in AOCI	10	10
Gross Unrealized Losses in AOCI	0	0
Total Fair Value	$ 151	$ 187