Investments in Securities - Available-for-sale Securities Gains (Losses) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Less than 12 consecutive months, gross unrealized losses	$ (3)	$ (13)
Less than 12 consecutive months, fair value	66	169
12 consecutive months or longer, gross unrealized losses	(26)	(10)
12 consecutive months or longer, fair value	238	159
Agency securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 consecutive months, gross unrealized losses	(3)	(12)
Less than 12 consecutive months, fair value	66	161
12 consecutive months or longer, gross unrealized losses	(26)	(10)
12 consecutive months or longer, fair value	238	159
Other mortgage-related securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 consecutive months, gross unrealized losses	0	(1)
Less than 12 consecutive months, fair value	0	8
12 consecutive months or longer, gross unrealized losses	0	0
12 consecutive months or longer, fair value	$ 0	$ 0