v3.25.4
Stock-Based Compensation - Summary of restricted stock awards (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Options and Restricted Stock Awards [Member]    
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expenses $ 14,213 $ 25,490
Atai ESOP [Member] | Options and Restricted Stock Awards [Member]    
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expenses 14,158 25,210
Atai HSOP [Member] | Options and Restricted Stock Awards [Member]    
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expenses   117
Other Subsidiaries Equity Plan    
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expenses 100 200
Other Subsidiaries Equity Plan | Options and Restricted Stock Awards [Member]    
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expenses 55 163
Research and Development | Options and Restricted Stock Awards [Member]    
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expenses 4,004 10,397
Research and Development | Atai ESOP [Member] | Options and Restricted Stock Awards [Member]    
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expenses 3,971 10,247
Research and Development | Atai HSOP [Member] | Options and Restricted Stock Awards [Member]    
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expenses   0
Research and Development | Other Subsidiaries Equity Plan | Options and Restricted Stock Awards [Member]    
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expenses 33 150
General and Administrative | Options and Restricted Stock Awards [Member]    
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expenses 10,209 15,093
General and Administrative | Atai ESOP [Member] | Options and Restricted Stock Awards [Member]    
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expenses 10,187 14,963
General and Administrative | Atai HSOP [Member] | Options and Restricted Stock Awards [Member]    
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expenses   117
General and Administrative | Other Subsidiaries Equity Plan | Options and Restricted Stock Awards [Member]    
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Stock-based compensation expenses $ 22 $ 13