v3.25.4
Fair Value - Recurring Changes in Fair Value (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Assets:    
Available-for-sale securities $ 375 $ 469
Total multifamily mortgage loans held for investment, at amortized cost $ 5,464 $ 3,744
Derivative Asset Statement Of Financial Position Extensible Enumeration Not Disclosed Flag Derivative assets Derivative assets
Derivative assets at fair value $ 177 $ 179
Derivative asset, gross amount offset $ (199) $ (362)
Liabilities:    
Derivative Liability Statement Of Financial Position Extensible Enumeration Not Disclosed Flag Derivative liabilities Derivative liabilities
Derivative liabilities at fair value $ 152 $ 154
Fannie Mae    
Liabilities:    
Long-term debt 256 385
Consolidated Trusts    
Liabilities:    
Long-term debt 15,060 13,292
Quoted Prices in Active Markets for Identical Assets (Level 1)    
Assets:    
Trading securities 55,205 77,610
Available-for-sale securities 0 0
Derivative assets at fair value 0 0
Liabilities:    
Derivative liabilities at fair value 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fannie Mae    
Liabilities:    
Long-term debt 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Consolidated Trusts    
Liabilities:    
Long-term debt 0 0
Significant Other Observable Inputs (Level 2)    
Assets:    
Trading securities 14,282 1,090
Available-for-sale securities 34 42
Derivative assets at fair value 304 487
Liabilities:    
Derivative liabilities at fair value 1,387 2,506
Significant Other Observable Inputs (Level 2) | Fannie Mae    
Liabilities:    
Long-term debt 104,784 129,152
Significant Other Observable Inputs (Level 2) | Consolidated Trusts    
Liabilities:    
Long-term debt 3,701,675 3,557,237
Significant Unobservable Inputs (Level 3)    
Assets:    
Trading securities 27 28
Available-for-sale securities 341 427
Derivative assets at fair value 72 54
Liabilities:    
Derivative liabilities at fair value 7 15
Significant Unobservable Inputs (Level 3) | Fannie Mae    
Liabilities:    
Long-term debt 602 567
Significant Unobservable Inputs (Level 3) | Consolidated Trusts    
Liabilities:    
Long-term debt 235 274
Recurring    
Assets:    
Trading securities 69,514 78,728
Available-for-sale securities 375 469
Total multifamily mortgage loans held for investment, at amortized cost 5,464 3,744
Derivative assets at fair value 177 179
Derivative asset, gross amount offset (199) (362)
Total assets at fair value 75,530 83,120
Liabilities:    
Long-term debt 15,316 13,677
Derivative liabilities at fair value 152 154
Derivative liabilities, gross amount offset (1,242) (2,367)
Total financial liabilities 15,468 13,831
Recurring | Mortgage-related securities    
Assets:    
Trading securities 14,291 1,098
Recurring | Non-mortgage-related securities    
Assets:    
Trading securities 55,223 77,630
Recurring | Agency    
Assets:    
Available-for-sale securities 308 339
Recurring | Other    
Assets:    
Available-for-sale securities 67 130
Recurring | Fannie Mae    
Liabilities:    
Long-term debt 256 385
Recurring | Consolidated Trusts    
Liabilities:    
Long-term debt 15,060 13,292
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)    
Assets:    
Trading securities 55,205 77,610
Available-for-sale securities 0 0
Total multifamily mortgage loans held for investment, at amortized cost 0 0
Derivative assets at fair value 0 0
Total assets at fair value 55,205 77,610
Liabilities:    
Long-term debt 0 0
Derivative liabilities at fair value 0 0
Total financial liabilities 0 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage-related securities    
Assets:    
Trading securities 0 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Non-mortgage-related securities    
Assets:    
Trading securities 55,205 77,610
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Agency    
Assets:    
Available-for-sale securities 0 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other    
Assets:    
Available-for-sale securities 0 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fannie Mae    
Liabilities:    
Long-term debt 0 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Consolidated Trusts    
Liabilities:    
Long-term debt 0 0
Recurring | Significant Other Observable Inputs (Level 2)    
Assets:    
Trading securities 14,282 1,090
Available-for-sale securities 34 42
Total multifamily mortgage loans held for investment, at amortized cost 5,076 3,345
Derivative assets at fair value 304 487
Total assets at fair value 19,696 4,964
Liabilities:    
Long-term debt 14,969 13,324
Derivative liabilities at fair value 1,387 2,506
Total financial liabilities 16,356 15,830
Recurring | Significant Other Observable Inputs (Level 2) | Mortgage-related securities    
Assets:    
Trading securities 14,264 1,070
Recurring | Significant Other Observable Inputs (Level 2) | Non-mortgage-related securities    
Assets:    
Trading securities 18 20
Recurring | Significant Other Observable Inputs (Level 2) | Agency    
Assets:    
Available-for-sale securities 32 38
Recurring | Significant Other Observable Inputs (Level 2) | Other    
Assets:    
Available-for-sale securities 2 4
Recurring | Significant Other Observable Inputs (Level 2) | Fannie Mae    
Liabilities:    
Long-term debt 0 136
Recurring | Significant Other Observable Inputs (Level 2) | Consolidated Trusts    
Liabilities:    
Long-term debt 14,969 13,188
Recurring | Significant Unobservable Inputs (Level 3)    
Assets:    
Trading securities 27 28
Available-for-sale securities 341 427
Total multifamily mortgage loans held for investment, at amortized cost 388 399
Derivative assets at fair value 72 54
Total assets at fair value 828 908
Liabilities:    
Long-term debt 347 353
Derivative liabilities at fair value 7 15
Total financial liabilities 354 368
Recurring | Significant Unobservable Inputs (Level 3) | Mortgage-related securities    
Assets:    
Trading securities 27 28
Recurring | Significant Unobservable Inputs (Level 3) | Non-mortgage-related securities    
Assets:    
Trading securities 0 0
Recurring | Significant Unobservable Inputs (Level 3) | Agency    
Assets:    
Available-for-sale securities 276 301
Recurring | Significant Unobservable Inputs (Level 3) | Other    
Assets:    
Available-for-sale securities 65 126
Recurring | Significant Unobservable Inputs (Level 3) | Fannie Mae    
Liabilities:    
Long-term debt 256 249
Recurring | Significant Unobservable Inputs (Level 3) | Consolidated Trusts    
Liabilities:    
Long-term debt $ 91 $ 104