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Summary of Significant Accounting Policies - Investments (Details) | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Dec. 31, 2023 USD ($) property | Dec. 31, 2022 USD ($) | Feb. 28, 2023 $ / shares | Jun. 30, 2022 | Dec. 31, 2021 | Mar. 31, 2017
Investment in available for sale securities |  |  |  |  |  |
Number of medical office and life science properties | property | 10 |  |  |  |  |
AlerisLife Inc |  |  |  |  |  |
Investment in available for sale securities |  |  |  |  |  |
Investment in equity securities acquisition, share price (in dollars per share) | $ / shares |  |  | $ 1.31 |  |  |
Corporate Joint Venture |  |  |  |  |  |
Investment in available for sale securities |  |  |  |  |  |
Principal amount of debt | $ 1,076,625,000 |  |  |  |  |
AlerisLife Inc | Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Carrying Amount |  |  |  |  |  |
Investment in available for sale securities |  |  |  |  |  |
Investments in Five Star | 0 | $ 5,880,000 |  |  |  |
Realized gain | $ 8,126,000 |  |  |  |  |
Unrealized loss |  | $ 25,660,000 |  |  |  |
Seaport Innovation LLC | Corporate Joint Venture |  |  |  |  |  |
Investment in available for sale securities |  |  |  |  |  |
Equity method investment ownership percentage | 10.00% |  |  | 20.00% | 20.00% | 55.00%
Principal amount of debt | $ 620,000,000 |  |  |  |  |
LSMD Fund REIT LLC | Corporate Joint Venture |  |  |  |  |  |
Investment in available for sale securities |  |  |  |  |  |
Equity method investment ownership percentage | 20.00% |  |  |  |  |
Principal amount of debt | $ 456,625,000 |  |  |  |  |

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