Annual report pursuant to Section 13 and 15(d)

Business Combination and Recapitalization - Additional Information (Detail)

v3.20.2
Business Combination and Recapitalization - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
May 12, 2020
Dec. 18, 2019
Sep. 29, 2019
Mar. 31, 2020
Mar. 31, 2025
Mar. 31, 2023
Jun. 15, 2020
May 14, 2020
Mar. 31, 2019
Business Acquisition [Line Items]                  
Business combination consideration   $ 420.9              
Business acquisition price per share   $ 10.00              
Closing of Share Price   13.88              
Business combination per share disclosed in fair value   $ 10.00              
Number of securities called by warrants or rights       5,750,000          
Earnout shares reserved for issuance       20,000,000          
Common stock to potential forfeiture in the event that the milestones are not achieved     1,800,000            
Business combination costs       $ 2.8          
Common share, shares outstanding       54,655,376         38,590,381
Common Stock, Shares, Issued       56,455,376         38,590,381
Preferred stock, shares outstanding       0          
Class of Warrant or Right, Outstanding       11,500,000          
Sponsor [Member]                  
Business Acquisition [Line Items]                  
Restricted Share For Each Milestone     900,000            
General and Administrative Expense [Member]                  
Business Acquisition [Line Items]                  
Additional Financial Advisory Fees       $ 2.3          
Forecast [Member] | Milestone Achievement One [Member]                  
Business Acquisition [Line Items]                  
Volume-weighted average price         $ 31.50 $ 17.50      
Subsequent Event [Member]                  
Business Acquisition [Line Items]                  
Restricted Share For Each Milestone 900,000                
Class of Warrant or Right, Outstanding             11,438,290 11,500,000  
Subsequent Event [Member] | Sponsor [Member]                  
Business Acquisition [Line Items]                  
Restricted Share For Each Milestone 900,000                
2018 Equity Incentive Plan [Member]                  
Business Acquisition [Line Items]                  
Options outstanding number   4,408,287   3,657,408          
Common stock [Member]                  
Business Acquisition [Line Items]                  
Number of shares issued in business combination   42,080,376   3,499,995          
Earnout shares reserved for issuance   20,000,000              
Common stock [Member] | Forecast [Member] | Milestone Achievement One [Member]                  
Business Acquisition [Line Items]                  
Earnout shares reserved for issuance         10,000,000 10,000,000      
Roivant Sciences Ltd. (RSL) [Member] | Common stock [Member] | Subsequent Event [Member]                  
Business Acquisition [Line Items]                  
Earnout Shares For Issuance 8,773,969                
Immunovant Sciences Ltd [Member]                  
Business Acquisition [Line Items]                  
Percentage of business acquisition   100.00%              
Number of shares issued in business combination   42,080,376              
Shares exchange ratio   0.48907%              
Immunovant Sciences Ltd [Member] | Common stock [Member] | Subsequent Event [Member]                  
Business Acquisition [Line Items]                  
Earnout Shares For Issuance 10,000,000                
Series A Preferred Stock [Member]                  
Business Acquisition [Line Items]                  
Number of shares issued in business combination   10,000              
Preferred stock, shares outstanding       10,000          
Series A Preferred Stock [Member] | Roivant Sciences Ltd. (RSL) [Member]                  
Business Acquisition [Line Items]                  
Number of shares issued in business combination   10,000