Net Income Per Share of Class A Common Stock - Schedule of Net Income Per Share of Class A Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net Income Attributable to PJT Partners Inc.	$ 6,945	$ 215	$ 12,181	$ 1,548
Dividends on Participating Securities	73		83
Net Income Attributable to Participating Securities	39		73
Class A Common Stock
Numerator:
Net Income Attributable to Shares of Class A Common Stock — Basic	6,833	215	12,025	1,548
Incremental Net Income from Dilutive Securities	378		496
Net Income Attributable to Shares of Class A Common Stock — Diluted	$ 7,211	$ 215	$ 12,521	$ 1,548
Denominator:
Weighted-Average Shares of Class A Common Stock Outstanding — Basic	22,641,562	18,825,696	20,987,863	18,654,187
Weighted-Average Shares of Class A Common Stock Outstanding — Diluted	24,185,020	18,825,696	22,689,344	18,654,187
Net Income Per Share of Class A Common Stock
Basic	$ 0.30	$ 0.01	$ 0.57	$ 0.08
Diluted	$ 0.30	$ 0.01	$ 0.55	$ 0.08
Class A Common Stock | Weighted-Average Unvested RSUs
Denominator:
Weighted-Average Number of Incremental Shares from Unvested RSUs	1,543,458		1,701,481