Net Loss per Share - Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Numerator:
Net loss attributable to Forge Global Holdings, Inc., basic	$ (18,342)	$ (18,348)	$ (50,690)	$ (64,425)
Net loss attributable to common stockholders, diluted	$ (18,342)	$ (18,348)	$ (50,690)	$ (64,425)
Denominator:
Weighted-average number of shares used to compute net loss per share attributable to common stockholders, basic (in shares)	184,158,571	173,957,880	182,261,198	173,045,721
Weighted-average number of shares used to compute net loss per share attributable to common stockholders, diluted (in shares)	184,158,571	173,957,880	182,261,198	173,045,721
Net loss per share attributable to Forge Global Holdings, Inc. common stockholders:
Basic (in dollars per share)	$ (0.10)	$ (0.11)	$ (0.28)	$ (0.37)
Diluted (in dollars per share)	$ (0.10)	$ (0.11)	$ (0.28)	$ (0.37)