Investments in Securities - Available-for-sale Securities 2 (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Consecutive Months, Gross Unrealized Losses in AOCI	$ (3)	$ (13)
Less than 12 Consecutive Months, Fair Value	92	169
12 Consecutive Months or Longer, Gross Unrealized Losses	(36)	(10)
12 Consecutive Months or Longer, Fair Value	271	159
Agency securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Consecutive Months, Gross Unrealized Losses in AOCI	(2)	(12)
Less than 12 Consecutive Months, Fair Value	78	161
12 Consecutive Months or Longer, Gross Unrealized Losses	(36)	(10)
12 Consecutive Months or Longer, Fair Value	271	159
Other mortgage-related
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Consecutive Months, Gross Unrealized Losses in AOCI	(1)	(1)
Less than 12 Consecutive Months, Fair Value	14	8
12 Consecutive Months or Longer, Gross Unrealized Losses	0	0
12 Consecutive Months or Longer, Fair Value	$ 0	$ 0