Summary of Significant Accounting Policies - Equity Securities (Details)	Dec. 31, 2019 shares
Class A Common Shares \| RMR Inc
Related Party Transaction [Line Items]
Common shares owned in RMR Inc. (in shares)	2,801,060

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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