Investments in Securities - Available-for-sale Securities 2 (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Consecutive Months, Gross Unrealized Losses in AOCI	$ (2)	$ (3)
Less than 12 Consecutive Months, Fair Value	73	66
12 Consecutive Months or Longer, Gross Unrealized Losses	(27)	(26)
12 Consecutive Months or Longer, Fair Value	232	238
Agency securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Consecutive Months, Gross Unrealized Losses in AOCI	(2)	(3)
Less than 12 Consecutive Months, Fair Value	70	66
12 Consecutive Months or Longer, Gross Unrealized Losses	(27)	(26)
12 Consecutive Months or Longer, Fair Value	232	238
Other mortgage-related
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Consecutive Months, Gross Unrealized Losses in AOCI	0	0
Less than 12 Consecutive Months, Fair Value	3	0
12 Consecutive Months or Longer, Gross Unrealized Losses	0	0
12 Consecutive Months or Longer, Fair Value	$ 0	$ 0