v3.25.2
Collaboration Agreements - Additional Information (Detail) - USD ($)
 1 Months Ended 3 Months Ended 6 Months Ended 12 Months Ended
Nov. 30, 2020
Jun. 30, 2018
Jan. 31, 2024
Jun. 30, 2025
Jun. 30, 2024
Dec. 31, 2023
Jun. 30, 2018
Jun. 30, 2025
Jun. 30, 2024
Dec. 31, 2023
Dec. 31, 2020
Dec. 31, 2024
Jun. 12, 2018
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Revenue       $ 31,660,000 $ 8,654,000     $ 45,724,000 $ 16,556,000        
Collaboration receivable - related party       16,270,000       16,270,000       $ 9,134,000  
Other Revenue [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Revenue       8,451,000 634,000     8,688,000 634,000        
Shionogi Collaboration Agreement [Member] | Other Revenue [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Revenue       8,100,000 600,000     8,100,000 600,000        
Shionogi Collaboration Agreement [Member] | SAGE-217 [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Upfront payment   $ 90,000,000.0                      
Average percentage on tiered royalties   20.00%                      
Revenue             $ 90,000,000.0            
Standalone selling price of license performance obligation   $ 90,000,000.0         90,000,000.0            
Shionogi Collaboration Agreement [Member] | SAGE-217 [Member] | Regulatory Milestones [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Future milestone payments                   $ 55,000,000.0      
Shionogi Collaboration Agreement [Member] | SAGE-217 [Member] | Maximum [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Additional milestone payment receivable   485,000,000.0         $ 485,000,000.0            
Shionogi Collaboration Agreement [Member] | SAGE-217 [Member] | Maximum [Member] | Regulatory Milestones [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Future milestone payments   70,000,000.0                      
Shionogi Collaboration Agreement [Member] | SAGE-217 [Member] | Maximum [Member] | Commercial Milestones [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Future milestone payments   30,000,000.0                      
Shionogi Collaboration Agreement [Member] | SAGE-217 [Member] | Maximum [Member] | Sales Milestones [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Future milestone payments   $ 385,000,000.0                      
Biogen Collaboration Agreement [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Collaboration agreement effective date Dec. 28, 2020                        
Upfront payment                     $ 875,000,000.0    
Revenue                     1,100,000,000    
Sale of stock, consideration received                     $ 1,500,000,000    
Issuance of common stock upon public offering, net of issuance costs, Shares                     6,241,473    
Purchase price                     $ 650,000,000    
Net reimbursement       (23,209,000) (7,420,000)     (37,036,000) (13,633,000)        
Payments to related parties               0          
Proceeds from related parties               17,400,000 93,100,000        
Biogen Collaboration Agreement [Member] | Related Party [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Collaboration receivable - related party       16,300,000       16,300,000       $ 9,100,000  
Biogen Collaboration Agreement [Member] | Other Revenue [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Revenue       400,000 0     600,000 0        
Biogen Collaboration Agreement [Member] | License And Milestone Revenue - Related Party [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Revenue       $ 0 $ 0 $ 75,000,000   $ 0 $ 0        
Milestone payments     $ 75,000,000                    
Biogen Collaboration Agreement [Member] | SAGE-217 [Member] | First Commercial Sale Of Zurzuvae For Treatment Of Women With Ppd [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Future milestone payments           150,000,000              
Milestone achieved           $ 75,000,000              
Biogen Collaboration Agreement [Member] | SAGE-217 [Member] | Maximum [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Additional milestone payment receivable                         $ 1,600,000,000
Biogen Collaboration Agreement [Member] | SAGE-217 [Member] | Maximum [Member] | First Commercial Sale of Zurzuvae for Treatment of MDD [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Future milestone payments $ 150,000,000                        
Biogen Collaboration Agreement [Member] | SAGE-217 [Member] | Maximum [Member] | First Commercial Sale Of Zurzuvae For Treatment Of Women With Ppd [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Future milestone payments 75,000,000                        
Biogen Collaboration Agreement [Member] | SAGE-217 [Member] | Maximum [Member] | Sales Milestones [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Future milestone payments 300,000,000                        
Biogen Collaboration Agreement [Member] | SAGE-217 [Member] | Maximum [Member] | Regulatory and Commercial Milestones [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Future milestone payments 475,000,000                        
Biogen Collaboration Agreement [Member] | SAGE-324 [Member] | Maximum [Member] | Sales Milestones [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Future milestone payments 300,000,000                        
Biogen Collaboration Agreement [Member] | SAGE-324 [Member] | Maximum [Member] | Regulatory and Commercial Milestones [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Future milestone payments $ 520,000,000                        
Biogen Stock Purchase Agreement [Member]                          
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                          
Upfront payment                     875,000,000    
Purchase price                     650,000,000    
Transaction price, total                     1,100,000,000    
Premium amount on equity investment                     $ 232,500,000    
Price per share                     $ 104.14    
Biogen stock purchase agreement, description               terminate on the earliest of (i) a specified regulatory milestone under the Biogen Collaboration Agreement, (ii) the date one year following the termination of the Biogen Collaboration Agreement and (iii) the seventh anniversary of the Effective Date.          
Stock issued                     $ 417,500,000