v3.26.1
Fair Value Measurements (Details) - USD ($)
$ in Thousands
 6 Months Ended
Jun. 30, 2026
Dec. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Securities Sold under Agreements to Repurchase $ 89,808,000 $ 85,286,000
Transfers between hierarchy levels no  
Agency securities $ 86,784,000 81,003,000
Non-Agency Securities, at Fair Value 94,000 95,000
Financial Instruments, Owned, Other, at Fair Value 573,000 606,000
U.S. Treasury securities 12,325,000 13,477,000
TBA securities (260,000) (169,000)
Derivative Liability 137,000 6,000
Debt of consolidated variable interest entities, at fair value 0 56,000
Obligation to return securities borrowed under reverse repurchase agreements, at fair value 18,150,000 16,452,000
Interest rate swaps 260,000 169,000
Mortgage Credit Investment Fund Limited Partnership 70,000 70,000
Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Agency securities 24,000 25,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets 12,367,000 13,488,000
Total liabilities 18,263,000 16,452,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets 87,599,000 81,877,000
Total liabilities 24,000 62,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Sale Of TBA And Forward Settling Agency Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Liability 24,000 6,000
Future [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Treasury Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
TBA securities 42,000 11,000
Derivative Liability (109,000) 0
Future [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | SOFR Futures Contracts    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
TBA securities 0  
Derivative Liability 4,000 0
Interest Rate Swaption [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Interest rate swaps 31,000 24,000
Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Interest rate swaps 111,000 57,000
Interest Rate Swap [Member] | Location, Statement of Financial Position, Balance [Axis]: agnc:AGNCDerivativeFinancialInstrumentsLiabilitiesMember | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Interest rate swaps 0 0
Purchases Of TBAs And Forward Settling Agency Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | TBA and Forward Settling Agency Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
TBA securities (76,000) $ (77,000)
Purchases Of TBAs And Forward Settling Agency Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Sale Of TBA And Forward Settling Agency Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
TBA securities $ (76,000)