Short-Term and Long-Term Debt - Characteristics of Debt (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Long-Term Debt by Year of Maturity [Abstract]
Total long-term debt	$ 4,211,684	$ 4,155,396
Assuming Callable Debt Redeemed at Next Available Call Date
Long-Term Debt by Year of Maturity [Abstract]
Total long-term debt	4,211,684
Fannie Mae
Long-Term Debt [Line Items]
Face amount	139,300	202,500
Long-Term Debt by Year of Maturity [Abstract]
2023	23,226
2024	18,951
2025	37,730
2026	9,189
2027	5,608
Thereafter	29,260
Total long-term debt	123,964	198,097
Fannie Mae | Zero-coupon debt
Long-Term Debt [Line Items]
Face amount	$ 10,000	$ 3,200
Effective interest rate	3.91%	0.66%
Fannie Mae | Callable
Long-Term Debt [Line Items]
Outstanding debt	$ 43,300	$ 47,000
Fannie Mae | Assuming Callable Debt Redeemed at Next Available Call Date
Long-Term Debt by Year of Maturity [Abstract]
2023	56,679
2024	13,712
2025	20,911
2026	6,795
2027	4,080
Thereafter	21,787
Total long-term debt	123,964
Consolidated Trusts
Long-Term Debt by Year of Maturity [Abstract]
Total long-term debt	4,087,720	$ 3,957,299
Consolidated Trusts | Assuming Callable Debt Redeemed at Next Available Call Date
Long-Term Debt by Year of Maturity [Abstract]
Total long-term debt	$ 4,087,720