v3.26.1
Cover Page - USD ($)
$ in Millions
 12 Months Ended
Mar. 31, 2026
May 20, 2026
Sep. 30, 2025
Entity Information [Line Items]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Mar. 31, 2026    
Current Fiscal Year End Date --03-31    
Document Transition Report false    
Entity File Number 001-39510    
Entity Registrant Name STEPSTONE GROUP INC.    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 84-3868757    
Entity Address, Address Line One 277 Park Avenue, 45th Floor    
Entity Address, City or Town New York    
Entity Address, State or Province NY    
Entity Address, Postal Zip Code 10172    
City Area Code 212    
Local Phone Number 351-6100    
Title of 12(b) Security Class A Common Stock, $0.001 par value per share    
Trading Symbol STEP    
Security Exchange Name NASDAQ    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction false    
Entity Shell Company false    
Entity Public Float     $ 5,111.5
Documents Incorporated by Reference Portions of the Registrant’s definitive proxy statement relating to its 2026 annual meeting of stockholders (the “2026 Proxy Statement”) are incorporated by reference into Part III of this annual report on Form 10-K where indicated. The 2026 Proxy Statement will be filed with the U.S. Securities and Exchange Commission within 120 days after the end of the fiscal year to which this report relates.    
Entity Central Index Key 0001796022    
Document Fiscal Year Focus 2026    
Document Fiscal Period Focus FY    
Amendment Flag false    
Class A Common Stock      
Entity Information [Line Items]      
Entity Common Stock, Shares Outstanding   80,706,668  
Class B Common Stock      
Entity Information [Line Items]      
Entity Common Stock, Shares Outstanding   38,637,761