Debt - Long-Term Debt (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Debt Instrument [Line Items]
Long-term Debt	$ 169,850	$ 169,296
Debt instrument recorded at fair value	5,971	5,841
Held by Freddie Mac
Debt Instrument [Line Items]
Par Value Of Long Term Debt	173,466	172,694
Long-term Debt	$ 169,850	$ 169,296
Long-term debt weighted average effective rate	4.03%	4.15%
Debt instrument recorded at fair value	$ 200	$ 200
Fixed Rate \| Held by Freddie Mac
Debt Instrument [Line Items]
Par Value Of Long Term Debt	102,753	92,236
Long-term Debt	$ 100,373	$ 90,104
Long-term debt weighted average effective rate	3.59%	3.62%
Fixed Rate \| Held by Freddie Mac \| Callable Medium Term Notes
Debt Instrument [Line Items]
Par Value Of Long Term Debt	$ 94,900	$ 84,400
Variable Rate \| Held by Freddie Mac
Debt Instrument [Line Items]
Par Value Of Long Term Debt	66,321	76,008
Long-term Debt	$ 66,301	$ 75,991
Long-term debt weighted average effective rate	4.64%	4.74%
Variable Rate \| Held by Freddie Mac \| Callable Medium Term Notes
Debt Instrument [Line Items]
Par Value Of Long Term Debt	$ 600	$ 700
Zero Coupon \| Held by Freddie Mac
Debt Instrument [Line Items]
Par Value Of Long Term Debt	3,904	3,904
Long-term Debt	$ 2,640	$ 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	$ 488	$ 546
Long-term Debt	$ 536	$ 591
Long-term debt weighted average effective rate	8.12%	8.95%