v3.25.4
Concentrations of Credit Risk - Other Concentrations (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Concentration Risk [Line Items]    
Estimated benefit included in combined loss reserves $ 1,200 $ 1,000
Receivable from claims on insured, defaulted loans excluding government insured loans 501 472
Allowance for mortgage insurance receivable 380 403
Single-family | Guaranty Book of Business    
Concentration Risk [Line Items]    
Primary mortgage insurance coverage risk in force 201,303 202,277
Pool mortgage insurance coverage risk in force 52 53
Mortgage insurance coverage risk in force $ 201,355 $ 202,330
Mortgage insurance coverage risk in force as a percentage of book of business 6.00% 6.00%
Single-family | Guaranty Book of Business | Credit Concentration Risk | Top five non-depository servicers    
Concentration Risk [Line Items]    
Concentration risk, percentage 62.00% 60.00%
Single-family | Guaranty Book of Business | Insurance Service Provider Concentration Risk    
Concentration Risk [Line Items]    
Concentration risk, percentage 100.00% 100.00%
Single-family | Guaranty Book of Business | Insurance Service Provider Concentration Risk | Mortgage Guaranty Insurance Corp.    
Concentration Risk [Line Items]    
Concentration risk, percentage 19.00% 19.00%
Single-family | Guaranty Book of Business | Insurance Service Provider Concentration Risk | Radian Guaranty, Inc.    
Concentration Risk [Line Items]    
Concentration risk, percentage 18.00% 18.00%
Single-family | Guaranty Book of Business | Insurance Service Provider Concentration Risk | Enact Mortgage Insurance Corp.    
Concentration Risk [Line Items]    
Concentration risk, percentage 17.00% 17.00%
Single-family | Guaranty Book of Business | Insurance Service Provider Concentration Risk | Arch Capital Group Ltd.    
Concentration Risk [Line Items]    
Concentration risk, percentage 16.00% 17.00%
Single-family | Guaranty Book of Business | Insurance Service Provider Concentration Risk | Essent Guaranty, Inc.    
Concentration Risk [Line Items]    
Concentration risk, percentage 16.00% 16.00%
Single-family | Guaranty Book of Business | Insurance Service Provider Concentration Risk | National Mortgage Insurance Corp.    
Concentration Risk [Line Items]    
Concentration risk, percentage 14.00% 13.00%
Single-family | Top five depository servicers | Guaranty Book of Business | Credit Concentration Risk | Top five depository servicers    
Concentration Risk [Line Items]    
Concentration risk, percentage 23.00% 24.00%
Single-family | Top five non-depository servicers | Guaranty Book of Business | Credit Concentration Risk | Top five non-depository servicers    
Concentration Risk [Line Items]    
Concentration risk, percentage 39.00% 36.00%
Single-family | Depository Servicer | Guaranty Book of Business | Credit Concentration Risk    
Concentration Risk [Line Items]    
Concentration risk, percentage 40.00% 42.00%
Single-family | Depository Servicer | Guaranty Book of Business | Credit Concentration Risk | Mr. Cooper and Rocket Mortgage, LLC    
Concentration Risk [Line Items]    
Concentration risk, percentage 23.00% 23.00%
Single-family | Non-Depository Servicer | Guaranty Book of Business | Credit Concentration Risk    
Concentration Risk [Line Items]    
Concentration risk, percentage 60.00% 58.00%
Multifamily    
Concentration Risk [Line Items]    
Maximum potential loss recovery from lenders under risk sharing agreements $ 129,600 $ 119,800
Multifamily | Guaranty Book of Business | Credit Concentration Risk | Top five non-depository servicers    
Concentration Risk [Line Items]    
Concentration risk, percentage 69.00% 70.00%
Multifamily | Guaranty Book of Business | Credit Concentration Risk | Walker & Dunlop, LLC    
Concentration Risk [Line Items]    
Concentration risk, percentage 13.00% 14.00%
Multifamily | Accounts Receivable | Credit Concentration Risk | Five Major Lenders    
Concentration Risk [Line Items]    
Concentration risk, percentage 53.00% 52.00%
Multifamily | Top five depository servicers | Guaranty Book of Business | Credit Concentration Risk | Top five depository servicers    
Concentration Risk [Line Items]    
Concentration risk, percentage 24.00% 26.00%
Multifamily | Top five non-depository servicers | Guaranty Book of Business | Credit Concentration Risk | Top five non-depository servicers    
Concentration Risk [Line Items]    
Concentration risk, percentage 45.00% 44.00%
Multifamily | Depository Servicer | Guaranty Book of Business | Credit Concentration Risk    
Concentration Risk [Line Items]    
Concentration risk, percentage 29.00% 31.00%
Multifamily | Non-Depository Servicer | Guaranty Book of Business | Credit Concentration Risk    
Concentration Risk [Line Items]    
Concentration risk, percentage 71.00% 69.00%