| Cover | Feb. 04, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Feb. 4, 2021 |
| Entity File Number | 001-38727 |
| Entity Registrant Name | PennyMac Financial Services, Inc. |
| Entity Central Index Key | 0001745916 |
| Entity Tax Identification Number | 83-1098934 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 3043 Townsgate Road |
| Entity Address, City or Town | Westlake Village |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 91361 |
| City Area Code | 818 |
| Local Phone Number | 224-7442 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.0001 par value |
| Trading Symbol | PFSI |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Entity Information, Former Legal or Registered Name | Not Applicable |
