Short-term and Long-term Debt - Long-Term Debt (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Debt Instrument [Line Items]
Long-term Debt	$ 156,998	$ 169,296
Long-Term Debt, Fair Value	177	195
Held by Freddie Mac
Debt Instrument [Line Items]
Par Value Of Long Term Debt	162,015	172,694
Long-term Debt	$ 156,998	$ 169,296
Long-term debt weighted average effective rate	3.97%	4.15%
Long-Term Debt, Fair Value	$ 200	$ 200
Fixed Rate \| Held by Freddie Mac
Debt Instrument [Line Items]
Par Value Of Long Term Debt	105,877	92,236
Long-term Debt	$ 102,031	$ 90,104
Long-term debt weighted average effective rate	3.67%	3.62%
Fixed Rate \| Held by Freddie Mac \| Callable Medium Term Notes
Debt Instrument [Line Items]
Par Value Of Long Term Debt	$ 98,000	$ 84,400
Variable Rate \| Held by Freddie Mac
Debt Instrument [Line Items]
Par Value Of Long Term Debt	50,582	76,008
Long-term Debt	$ 50,554	$ 75,991
Long-term debt weighted average effective rate	4.49%	4.74%
Variable Rate \| Held by Freddie Mac \| Callable Medium Term Notes
Debt Instrument [Line Items]
Par Value Of Long Term Debt	$ 900	$ 700
Zero Coupon \| Held by Freddie Mac
Debt Instrument [Line Items]
Par Value Of Long Term Debt	3,904	3,904
Long-term Debt	$ 2,703	$ 2,610
Long-term debt weighted average effective rate	4.74%	4.73%
Other \| Held by Freddie Mac
Debt Instrument [Line Items]
Par Value Of Long Term Debt	$ 1,652	$ 546
Long-term Debt	$ 1,710	$ 591
Long-term debt weighted average effective rate	6.23%	8.95%