XML 17 R1.htm IDEA: XBRL DOCUMENT v3.20.2
Cover Page - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Nov. 19, 2020
Mar. 31, 2020
Document Information [Line Items]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Sep. 30, 2020    
Document Transition Report false    
Entity File Number 001-37616    
Entity Registrant Name RMR GROUP INC.    
Entity Incorporation, State or Country Code MD    
Entity Tax Identification Number 47-4122583    
Entity Address, Address Line One Two Newton Place    
Entity Address, Address Line Two 255 Washington Street    
Entity Address, Address Line Three Suite 300    
Entity Address, City or Town Newton    
Entity Address, State or Province MA    
Entity Address, Postal Zip Code 02458-1634    
City Area Code 617    
Local Phone Number 796-8230    
Title of 12(b) Security Class A common stock, $0.001 par value per share    
Trading Symbol RMR    
Security Exchange Name NASDAQ    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company true    
Entity Ex Transition Period true    
Entity Shell Company false    
Entity Public Float     $ 406.2
Amendment Flag false    
Entity Central Index Key 0001644378    
Current Fiscal Year End Date --09-30    
Document Fiscal Year Focus 2020    
Document Fiscal Period Focus FY    
Documents Incorporated by Reference
DOCUMENTS INCORPORATED BY REFERENCE
Portions of the Registrant’s definitive proxy statement for its 2021 annual meeting of shareholders are incorporated by reference in Part III of this Form 10- K.
    
Class A common shares      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   15,395,641  
Class B-1 common shares      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   1,000,000  
Class B-2 common shares      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   15,000,000