Investments in Securities - Maturity Information (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Total Carrying Amount
Total Carrying Amount, Net	$ 741
One Year or Less	3
After One Year Through Five Years	22
After Five Years Through Ten Years	27
After Ten Years	689
Total Fair Value
Total Fair Value	741	$ 837
One Year or Less	3
After One Year Through Five Years	22
After Five Years Through Ten Years	28
After Ten Years	688
Agency securities
Total Carrying Amount
Total Carrying Amount, Net	459
One Year or Less	0
After One Year Through Five Years	4
After Five Years Through Ten Years	13
After Ten Years	442
Total Fair Value
Total Fair Value	453	507
One Year or Less	0
After One Year Through Five Years	4
After Five Years Through Ten Years	13
After Ten Years	436
Other mortgage-related securities
Total Carrying Amount
Total Carrying Amount, Net	282
One Year or Less	3
After One Year Through Five Years	18
After Five Years Through Ten Years	14
After Ten Years	247
Total Fair Value
Total Fair Value	288	$ 330
One Year or Less	3
After One Year Through Five Years	18
After Five Years Through Ten Years	15
After Ten Years	$ 252