Net Loss Per Share - Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Numerator:
Net loss attributable to Forge Global Holdings, Inc., basic	$ (18,348)	$ (16,198)	$ (64,425)	$ (85,741)
Decrease in fair value of public warrants	0	(3,937)	0	(3,897)
Net loss attributable to common stockholders, diluted	$ (18,348)	$ (20,135)	$ (64,425)	$ (89,638)
Denominator:
Weighted-average number of shares used to compute net loss per share attributable to common stockholders, basic (in shares)	173,957,880	169,838,778	173,045,721	134,683,950
Weighted-average number of shares used to compute net loss per share attributable to common stockholders, diluted (in shares)	173,957,880	170,209,256	173,045,721	135,960,612
Net loss per share attributable to Forge Global Holdings, Inc. common stockholders:
Basic (in dollars per share)	$ (0.11)	$ (0.10)	$ (0.37)	$ (0.64)
Diluted (in dollars per share)	$ (0.11)	$ (0.12)	$ (0.37)	$ (0.66)