| Document and Entity Information | Oct. 27, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 27, 2020 |
| Entity Registrant Name | PJT Partners Inc. |
| Entity Central Index Key | 0001626115 |
| Entity Emerging Growth Company | false |
| Entity File Number | 001-36869 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 36-4797143 |
| Entity Address, Address Line One | 280 Park Avenue |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10017 |
| City Area Code | (212) |
| Local Phone Number | 364-7800 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of each class | Class A common stock, par value $0.01 per share |
| Trading Symbol(s) | PJT |
| Name of each exchange on which registered | NYSE |
