Investments in Securities - Available-for-sale Securities 2 (Details) - Agency securities - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Consecutive Months, Gross Unrealized Losses in AOCI	$ (1)	$ (3)
Less than 12 Consecutive Months, Fair Value	41	66
12 Consecutive Months or Longer, Gross Unrealized Losses	(24)	(26)
12 Consecutive Months or Longer, Fair Value	$ 233	$ 238