Organization and Basis of Presentation - Summary of New Common Stock Outstanding (Details)	Dec. 31, 2021 shares	Dec. 30, 2021 shares	Dec. 31, 2020 shares	Dec. 31, 2019 shares
Schedule Of Reverse Recapitalization [Line Items]
Common stock, shares outstanding	183,367,037	183,367,000	8,160,828
Options outstanding (in shares)	40,828,158		30,752,163	16,161,311
Public Warrants
Schedule Of Reverse Recapitalization [Line Items]
Number of securities called by warrants (in shares)		8,600,000
Stock options
Schedule Of Reverse Recapitalization [Line Items]
Options outstanding (in shares)		40,800,000
Restricted stock units
Schedule Of Reverse Recapitalization [Line Items]
Unvested equity instrument outstanding (in shares)	4,440,067	4,400,000	0
Restricted shares
Schedule Of Reverse Recapitalization [Line Items]
Unvested equity instrument outstanding (in shares)	481,301	500,000
Heliogen Stockholders
Schedule Of Reverse Recapitalization [Line Items]
Common stock, shares outstanding		154,819,000
Athena Public Stockholders
Schedule Of Reverse Recapitalization [Line Items]
Common stock, shares outstanding		2,271,000
Sponsor Shareholders
Schedule Of Reverse Recapitalization [Line Items]
Private placement unit, number of common stock per unit		1
Private placement unit, number of warrants per unit		0.33
Sponsor Shareholders | Athena’s founder shares and private placement units
Schedule Of Reverse Recapitalization [Line Items]
Common stock, shares outstanding		9,267,000
Sponsor Shareholders | Anti-dilutive rights waived
Schedule Of Reverse Recapitalization [Line Items]
Common stock, shares outstanding		510,000
PIPE Investors
Schedule Of Reverse Recapitalization [Line Items]
Common stock, shares outstanding		16,500,000
Heliogen, Inc.
Schedule Of Reverse Recapitalization [Line Items]
Ownership percentage		100.00%
Heliogen, Inc. | Heliogen Stockholders
Schedule Of Reverse Recapitalization [Line Items]
Ownership percentage		84.40%
Heliogen, Inc. | Athena Public Stockholders
Schedule Of Reverse Recapitalization [Line Items]
Ownership percentage		1.20%
Heliogen, Inc. | Sponsor Shareholders | Athena’s founder shares and private placement units
Schedule Of Reverse Recapitalization [Line Items]
Ownership percentage		5.10%
Heliogen, Inc. | Sponsor Shareholders | Anti-dilutive rights waived
Schedule Of Reverse Recapitalization [Line Items]
Ownership percentage		0.30%
Heliogen, Inc. | PIPE Investors
Schedule Of Reverse Recapitalization [Line Items]
Ownership percentage		9.00%