Securitizations and Variable Interest Entities - Non-Consolidated VIEs (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Assets [Abstract]
Investments in securities, at fair value	$ 85,412	$ 55,771
Other Assets	26,566	21,333
Assets	3,497,598	3,386,692
Outstanding balance of the guarantor advance	400	300
Liabilities [Abstract]
Other liabilities	11,595	12,346
Variable Interest Entity, Not Primary Beneficiary
Assets [Abstract]
Investments in securities, at fair value	12,006	12,055
Other Assets	5,257	5,522
Assets	487,914	518,307
Maximum Exposure to Loss	422,902	446,702
Liabilities [Abstract]
Other liabilities	5,120	5,724
Variable Interest Entity, Not Primary Beneficiary | Other
Assets [Abstract]
Investments in securities, at fair value	0	0
Other Assets	7	7
Assets	64	79
Maximum Exposure to Loss	15	79
Liabilities [Abstract]
Other liabilities	0	0
Variable Interest Entity, Not Primary Beneficiary | Single Family Guarantee Segment
Assets [Abstract]
Investments in securities, at fair value	6,954	6,792
Other Assets	333	315
Assets	152,832	161,382
Maximum Exposure to Loss	123,364	128,990
Liabilities [Abstract]
Other liabilities	1,307	1,335
Variable Interest Entity, Not Primary Beneficiary | Single Family Guarantee Segment | Securitization products
Assets [Abstract]
Investments in securities, at fair value	1,451	1,633
Other Assets	162	157
Assets	30,025	30,038
Maximum Exposure to Loss	24,604	24,470
Liabilities [Abstract]
Other liabilities	498	458
Variable Interest Entity, Not Primary Beneficiary | Single Family Guarantee Segment | Guarantees of Fannie Mae securities
Assets [Abstract]
Investments in securities, at fair value	5,503	5,159
Other Assets	74	69
Assets	98,370	104,120
Maximum Exposure to Loss	98,754	104,513
Liabilities [Abstract]
Other liabilities	675	706
Variable Interest Entity, Not Primary Beneficiary | Single Family Guarantee Segment | CRT products
Assets [Abstract]
Investments in securities, at fair value	0	0
Other Assets	97	89
Assets	24,437	27,224
Maximum Exposure to Loss	6	7
Liabilities [Abstract]
Other liabilities	134	171
Variable Interest Entity, Not Primary Beneficiary | Multifamily Segment
Assets [Abstract]
Investments in securities, at fair value	5,052	5,263
Other Assets	4,917	5,200
Assets	335,018	356,846
Maximum Exposure to Loss	299,523	317,633
Liabilities [Abstract]
Other liabilities	3,813	4,389
Variable Interest Entity, Not Primary Beneficiary | Multifamily Segment | Securitization products
Assets [Abstract]
Investments in securities, at fair value	5,052	5,263
Other Assets	4,886	5,171
Assets	332,572	355,108
Maximum Exposure to Loss	299,507	317,611
Liabilities [Abstract]
Other liabilities	3,792	4,374
Variable Interest Entity, Not Primary Beneficiary | Multifamily Segment | CRT products
Assets [Abstract]
Investments in securities, at fair value	0	0
Other Assets	31	29
Assets	2,446	1,738
Maximum Exposure to Loss	16	22
Liabilities [Abstract]
Other liabilities	$ 21	$ 15