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Summary of Significant Accounting Policies - Investments (Details) $ / shares in Units, $ in Thousands | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Jun. 30, 2017 USD ($) | Dec. 31, 2016 USD ($) $ / shares | Dec. 31, 2019 USD ($) shares | Dec. 31, 2018 USD ($) shares | Dec. 31, 2017 USD ($) | Jun. 30, 2019 shares
Investment in available for sale securities |  |  |  |  |  |
Unrealized gains (losses) on equity securities, net |  |  | $ (41,898) | $ (20,724) | $ 0 |
Impairment of assets |  |  | 115,201 | 66,346 | $ 5,082 |
Class A common shares | RMR Inc. |  |  |  |  |  |
Investment in available for sale securities |  |  |  |  |  |
Investment in common shares (in shares) | shares |  |  |  |  |  | 2,637,408
Five Star |  |  |  |  |  |
Investment in available for sale securities |  |  |  |  |  |
Impairment of assets |  | $ 2,795 |  |  |  |
Weighted average quoted market prices (in dollars per share) | $ / shares |  | $ 2.70 |  |  |  |
Five Star |  |  |  |  |  |
Investment in available for sale securities |  |  |  |  |  |
Fair value of investment |  |  | 1,571 | 2,033 |  |
Unrealized gains (losses) on equity securities, net |  |  | $ (462) | $ (4,320) |  |
Impairment of assets | $ 5,082 |  |  |  |  |
Five Star | Common Shares |  |  |  |  |  |
Investment in available for sale securities |  |  |  |  |  |
Investment in common shares (in shares) | shares |  |  | 423,500 | 423,500 |  |
Reverse stock split ratio |  |  | 0.1 | 0.1 |  |
Cost basis for shares owned |  |  | $ 6,353 |  |  |

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