Unaudited Condensed Consolidated Statements of Changes in Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands		Total	Series B-1	Previously Reported	Revision of Prior Period, Adjustment	Common Stock	Common Stock Previously Reported	Common Stock Revision of Prior Period, Adjustment	Additional Paid-In Capital	Additional Paid-In Capital Previously Reported	Additional Paid-In Capital Revision of Prior Period, Adjustment	Accumulated Deficit	Accumulated Deficit Previously Reported
Beginning balance (in shares) at Dec. 31, 2020		49,084,184		15,717,345	33,366,839
Beginning balance at Dec. 31, 2020		$ 156,848		$ 156,848
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of Series B-1 convertible preferred stock upon conversion of convertible notes and accrued interest (in shares)		27,947
Issuance of Series B-1 convertible preferred stock upon conversion of convertible notes and accrued interest		$ 111
Ending balance (in shares) at Mar. 31, 2021		49,112,131
Ending balance at Mar. 31, 2021		$ 156,959
Beginning balance (in shares) at Dec. 31, 2020						71,119,686	22,773,377	48,346,309
Beginning balance at Dec. 31, 2020		(7,499)		$ (7,499)					$ 52,561	$ 52,561		$ (60,060)	$ (60,060)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class AA common stock upon exercise of vested stock options, including stock options exercised via promissory notes (in shares)						473,658
Issuance of Class AA common stock upon exercise of vested stock options, including stock options exercised via promissory notes		168							168
Issuance of Class AA common stock upon early exercise of unvested stock options (in shares)						1,672,270
Vesting of early exercised stock options and restricted stock awards		11							11
Stock-based compensation expense		1,259							1,259
Net loss		938										938
Ending balance (in shares) at Mar. 31, 2021						73,265,614
Ending balance at Mar. 31, 2021		$ (5,123)							53,999			(59,122)
Beginning balance (in shares) at Dec. 31, 2020		49,084,184		15,717,345	33,366,839
Beginning balance at Dec. 31, 2020		$ 156,848		$ 156,848
Ending balance (in shares) at Dec. 31, 2021		73,914,149	42,133,496	23,668,198	50,245,951
Ending balance at Dec. 31, 2021		$ 246,056	$ 150,553	$ 246,056
Beginning balance (in shares) at Dec. 31, 2020						71,119,686	22,773,377	48,346,309
Beginning balance at Dec. 31, 2020		(7,499)		(7,499)					52,561	52,561		(60,060)	(60,060)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unissued common stock (in shares)	[1]							(210,302)
Ending balance (in shares) at Dec. 31, 2021						63,090,701	20,269,864	43,031,139
Ending balance at Dec. 31, 2021		$ (52,640)		$ (52,640)		$ 5		$ 5	25,914	$ 25,919	$ (5)	(78,559)	$ (78,559)
Increase (Decrease) in Temporary Equity [Roll Forward]
Conversion of preferred stock to common stock (in shares)		(73,914,149)
Conversion of preferred stock to common stock		$ (246,056)
Ending balance (in shares) at Mar. 31, 2022		0
Ending balance at Mar. 31, 2022		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Pre-close exercise of vested options (in shares)						190,505
Pre-close exercise of vested options		102							102
Pre-close exercise of unvested options (in shares)						4,472
Pre-close exercise of unvested options
Pre-close issuance common stock for services (in shares)						62,952
Pre-close issuance common stock for services		621							621
Conversion of preferred stock to common stock (in shares)						73,914,149
Conversion of preferred stock to common stock		246,056				$ 7			246,049
Conversion of May 2020 and October 2020 preferred stock warrants of Legacy Forge to common stock warrants		2,949							2,949
Issuance of common stock upon settlement of promissory notes		4,207				$ 2			4,205
Issuance of common stock upon Merger (net of redemptions), including PIPE and A&R FPA investors, net of transaction costs (in shares)						31,961,047
Issuance of common stock upon Merger (net of redemptions), including PIPE and A&R FPA investors, net of transaction costs		$ 140,811				$ 3			140,808
Issuance of Class AA common stock upon exercise of vested stock options, including stock options exercised via promissory notes (in shares)		194,977
Vesting of early exercised stock options and restricted stock awards		$ 409							409
Stock-based compensation expense		7,948							7,948
Net loss		(64,424)										(64,424)
Ending balance (in shares) at Mar. 31, 2022						169,223,826
Ending balance at Mar. 31, 2022		$ 286,039				$ 17			$ 429,005			$ (142,983)

[1] (1) This amount represents shares that were not issued upon the closing of the Merger (see Note 3) as a result of a shareholder’s demand for appraisal rights. If the appraisal rights demand is withdrawn or not perfected with the Delaware Court of Chancery, these shares will be issued to the shareholder.