Debt - Other Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Long-term Debt Carrying Amount	$ 169,296	$ 167,333
Held by Freddie Mac
Debt Instrument [Line Items]
Other long-term debt par value	172,694	172,943
Long-term Debt Carrying Amount	$ 169,296	$ 167,333
Long-term debt weighted average effective rate	4.15%	3.65%
Debt instruments recorded at fair value	$ 200	$ 300
Held by Freddie Mac | Other
Debt Instrument [Line Items]
Other long-term debt par value	546	1,324
Long-term Debt Carrying Amount	$ 591	$ 1,371
Long-term debt weighted average effective rate	8.95%	10.90%
Held by Freddie Mac | Fixed-rate
Debt Instrument [Line Items]
Other long-term debt par value	$ 92,236	$ 130,965
Long-term Debt Carrying Amount	$ 90,104	$ 126,815
Long-term debt weighted average effective rate	3.62%	3.09%
Held by Freddie Mac | Fixed-rate | Medium-term notes - callable
Debt Instrument [Line Items]
Other long-term debt par value	$ 84,400	$ 112,600
Held by Freddie Mac | Variable-rate
Debt Instrument [Line Items]
Other long-term debt par value	76,008	35,906
Long-term Debt Carrying Amount	$ 75,991	$ 35,893
Long-term debt weighted average effective rate	4.74%	5.16%
Held by Freddie Mac | Variable-rate | Medium-term notes - callable
Debt Instrument [Line Items]
Other long-term debt par value	$ 700	$ 1,300
Held by Freddie Mac | Zero-coupon
Debt Instrument [Line Items]
Other long-term debt par value	3,904	4,748
Long-term Debt Carrying Amount	$ 2,610	$ 3,254
Long-term debt weighted average effective rate	4.73%	6.22%