v3.24.0.1
Stock Option and Grant Plan - Additional Information (Details) - USD ($)
 1 Months Ended 12 Months Ended
Feb. 29, 2020
May 31, 2019
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Oct. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Stock-based compensation expense     $ 98,647,000 $ 84,321,000 $ 43,570,000  
Weighted-average grant date fair value per share of stock options granted     $ 27.88 $ 40.86 $ 58.56  
Aggregate intrinsic value of stock options exercised     $ 20,000,000 $ 23,400,000 $ 85,100,000  
Weighted-average exercise price of stock options     $ 7.69 $ 5.64 $ 9.88  
Employee Stock Option            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Unrecognized compensation cost related to unvested stock options     $ 111,500,000      
Unrecognized compensation cost, cost to recognize over a weighted-average period     2 years 3 months 18 days      
Performance-based Stock Options            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Stock-based compensation expense     $ 0      
Restricted Stock            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Unrecognized compensation cost, cost to recognize over a weighted-average period     2 years 2 months 12 days      
Aggregate fair value of restricted shares vested     $ 13,800,000 $ 53,100,000 $ 6,400,000  
Unrecognized stock-based compensation expense, expected to vest     $ 72,800,000      
Restricted Stock | Maximum            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Vesting period     4 years      
Restricted Stock | Minimum            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Vesting period     2 years      
2017 Plan | Stock Options and Restricted Stock | Employees, Officers, Founders and Consultants            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Vesting period   4 years        
2017 Plan | Employee Stock Option            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Expiration period   10 years        
2017 Plan | Non-Statutory Options | Employees, Officers, Board of Directors and Consultants            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Vesting period   4 years        
2019 Plan            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Maximum number of shares for future issuance           3,700,000
Number of shares reserved for future issuance     12,376,374      
Number of shares available for future issuance     1,173,189      
2019 Plan | Common Stock | Maximum            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Annual percentage increase in shares authorized     4.00%      
2019 Plan | From 2017 Plan Shares | Maximum            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Maximum number of shares for future issuance           5,639,818
2019 Employee Stock Purchase Plan            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Number of shares available for future issuance     2,247,569      
Number of shares issued     130,403 70,073 0  
Stock-based compensation expense     $ 1,300,000 $ 1,500,000 $ 300,000  
Common stock, shares description In February 2020, the Company’s board of directors adopted the Beam Therapeutics Inc. 2019 Employee Stock Purchase Plan, or ESPP, which was approved by the Company’s stockholders. Pursuant to the ESPP, certain employees of the Company, excluding consultants and non-employee directors, are eligible to purchase common stock of the Company at a reduced rate during offering periods. The ESPP permits participants to purchase common stock using funds contributed through payroll deductions, subject to a calendar year limit of $25,000 and at a purchase price of 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the applicable purchase date, which will be the final trading day of the applicable purchase period.          
Maximum amount allowed to purchase common stock using payroll deduction $ 25,000          
Percentage of common stock purchase price lower of the fair market value 85.00%