| Document and Entity Information | Jul. 29, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Jul. 29, 2021 |
| Entity Registrant Name | Federal Home Loan Mortgage Corporation |
| Entity File Number | 001-34139 |
| Entity Tax Identification Number | 52-0904874 |
| Entity Address, Address Line One | 8200 Jones Branch Drive |
| Entity Address, City or Town | McLean, |
| Entity Address, State or Province | VA |
| Entity Address, Postal Zip Code | 22102-3110 |
| City Area Code | 703 |
| Local Phone Number | 903-2000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001026214 |
| Amendment Flag | false |
| Entity Incorporation, State or Country Code | X1 |
