Net Loss Per Share Attributable to Common Stockholders - Weighted-Average Common Stock Equivalents Excluded from Calculation of Diluted Net Income (Loss) Per Share as They Had Anti-Dilutive Effect (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Preferred stock (if converted)		7,020,044		6,771,176
Employee Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Preferred stock (if converted)	403,686	408,782	412,934	406,596
Vaccinex Products, LP Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Preferred stock (if converted)	1,202,566	1,202,566	1,202,566	1,202,566
VX3 Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Preferred stock (if converted)	1,318,797		1,103,825