Debt - Long-Term Debt (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Debt instrument recorded at fair value	$ 2,693	$ 2,339
Held by Freddie Mac
Debt Instrument [Line Items]
Par Value Of Long Term Debt	176,782	172,943
Long-term Debt	$ 172,659	$ 167,333
Long-term debt weighted average effective rate	3.76%	3.65%
Debt instrument recorded at fair value	$ 200	$ 300
Fixed Rate \| Held by Freddie Mac
Debt Instrument [Line Items]
Par Value Of Long Term Debt	124,173	130,965
Long-term Debt	$ 121,423	$ 126,815
Long-term debt weighted average effective rate	3.18%	3.09%
Fixed Rate \| Held by Freddie Mac \| Callable Medium Term Notes
Debt Instrument [Line Items]
Par Value Of Long Term Debt	$ 108,800	$ 112,600
Variable Rate \| Held by Freddie Mac
Debt Instrument [Line Items]
Par Value Of Long Term Debt	47,075	35,906
Long-term Debt	$ 47,067	$ 35,893
Long-term debt weighted average effective rate	4.99%	5.16%
Variable Rate \| Held by Freddie Mac \| Callable Medium Term Notes
Debt Instrument [Line Items]
Par Value Of Long Term Debt	$ 1,300	$ 1,300
Zero Coupon \| Held by Freddie Mac
Debt Instrument [Line Items]
Par Value Of Long Term Debt	4,748	4,748
Long-term Debt	$ 3,354	$ 3,254
Long-term debt weighted average effective rate	6.25%	6.22%
Other \| Held by Freddie Mac
Debt Instrument [Line Items]
Par Value Of Long Term Debt	$ 786	$ 1,324
Long-term Debt	$ 815	$ 1,371
Long-term debt weighted average effective rate	10.17%	10.90%