Investments in Securities - Maturity Information (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Total Carrying Amount
Total Carrying Amount, Net	$ 764	$ 827
One Year or Less	4
After One Year Through Five Years	23
After Five Years Through Ten Years	29
After Ten Years	708
Total Fair Value
Total Fair Value	765	837
One Year or Less	4
After One Year Through Five Years	23
After Five Years Through Ten Years	30
After Ten Years	708
Fannie Mae
Total Carrying Amount
Total Carrying Amount, Net	461	492
One Year or Less	0
After One Year Through Five Years	3
After Five Years Through Ten Years	13
After Ten Years	445
Total Fair Value
Total Fair Value	458	495
One Year or Less	0
After One Year Through Five Years	3
After Five Years Through Ten Years	14
After Ten Years	441
Other agency
Total Carrying Amount
Total Carrying Amount, Net	10	12
One Year or Less	0
After One Year Through Five Years	0
After Five Years Through Ten Years	1
After Ten Years	9
Total Fair Value
Total Fair Value	10	12
One Year or Less	0
After One Year Through Five Years	0
After Five Years Through Ten Years	1
After Ten Years	9
Other mortgage-related securities
Total Carrying Amount
Total Carrying Amount, Net	293	323
One Year or Less	4
After One Year Through Five Years	20
After Five Years Through Ten Years	15
After Ten Years	254
Total Fair Value
Total Fair Value	297	$ 330
One Year or Less	4
After One Year Through Five Years	20
After Five Years Through Ten Years	15
After Ten Years	$ 258