Related Person Transactions	3 Months Ended
Mar. 31, 2019
Related Party Transactions [Abstract]
Related Person Transactions	Related Person Transactions We have relationships and historical and continuing transactions with Five Star, RMR LLC, RMR Inc., Affiliates Insurance Company, or AIC, and others related to them, including other companies to which RMR LLC provides management services and which have trustees, directors and officers who are also our Trustees or officers. Five Star. We are currently one of Five Star’s largest stockholders. As of March 31, 2019, we owned 4,235,000 of Five Star’s common shares, or approximately 8.3% of Five Star’s outstanding common shares. Five Star is our largest tenant and the manager of our managed senior living communities. RMR LLC provides management services to both us and Five Star. As of March 31, 2019, ABP Acquisition LLC, a subsidiary of ABP Trust, the controlling shareholder of RMR Inc., owned 35.4% of Five Star's outstanding common shares. Adam D. Portnoy, one of our Managing Trustees, is the sole trustee of ABP Trust and a managing director of Five Star. Five Star’s president and chief executive officer and executive vice president, chief financial officer and treasurer are officers and employees of RMR LLC. On April 1, 2019, we entered into the Transaction Agreement, pursuant to which we agreed to modify our existing business arrangements with Five Star, subject to certain conditions and the receipt of various approvals. See Notes 9 and 14 for further information regarding our relationships, agreements and transactions with Five Star and Note 5 for further information regarding our investment in Five Star. Our Manager, RMR LLC. We have two agreements with RMR LLC to provide management services to us. See Note 10 for further information regarding our management agreements with RMR LLC. RMR Inc. RMR LLC is a majority owned subsidiary of RMR Inc. and RMR Inc. is the managing member of RMR LLC. Adam D. Portnoy, one of our Managing Trustees, is the sole trustee, an officer and the controlling shareholder of ABP Trust, which is the controlling shareholder of RMR Inc., a managing director, president and chief executive officer of RMR Inc., and an officer and employee of RMR LLC. Jennifer B. Clark, our other Managing Trustee, also serves as a managing director and as executive vice president, general counsel and secretary of RMR Inc. and an officer of ABP Trust and RMR LLC. Other officers and employees of RMR LLC also serve as our officers. As of March 31, 2019, we owned 2,637,408 shares of class A common stock of RMR Inc. See Note 5 for further information regarding our investment in RMR Inc. AIC. We, ABP Trust, Five Star and four other companies to which RMR LLC provides management services currently own AIC in equal amounts. We (including our consolidated joint venture) and the other AIC shareholders participate in a combined property insurance program arranged and reinsured in part by AIC. As of March 31, 2019 and December 31, 2018, our investment in AIC had a carrying value of $9,102 and $8,632, respectively. These amounts are included in other assets in our condensed consolidated balance sheets. We recognized income related to our investment in AIC, which is presented as equity in earnings of an investee in our condensed consolidated statements of comprehensive income. Our other comprehensive income includes our proportionate part of unrealized gains on securities that are owned by AIC related to our investment in AIC. For further information about these and other such relationships and certain other related person transactions, refer to our Annual Report.

Related Person Transactions

We have relationships and historical and continuing transactions with Five Star, RMR LLC, RMR Inc., Affiliates Insurance Company, or AIC, and others related to them, including other companies to which RMR LLC provides management services and which have trustees, directors and officers who are also our Trustees or officers.

Five Star. We are currently one of Five Star’s largest stockholders. As of March 31, 2019, we owned 4,235,000 of Five Star’s common shares, or approximately 8.3% of Five Star’s outstanding common shares. Five Star is our largest tenant and the manager of our managed senior living communities. RMR LLC provides management services to both us and Five Star. As of March 31, 2019, ABP Acquisition LLC, a subsidiary of ABP Trust, the controlling shareholder of RMR Inc., owned 35.4% of Five Star's outstanding common shares. Adam D. Portnoy, one of our Managing Trustees, is the sole trustee of ABP Trust and a managing director of Five Star. Five Star’s president and chief executive officer and executive vice president, chief financial officer and treasurer are officers and employees of RMR LLC. On April 1, 2019, we entered into the Transaction Agreement, pursuant to which we agreed to modify our existing business arrangements with Five Star, subject to certain conditions and the receipt of various approvals. See Notes 9 and 14 for further information regarding our relationships, agreements and transactions with Five Star and Note 5 for further information regarding our investment in Five Star.

Our Manager, RMR LLC. We have two agreements with RMR LLC to provide management services to us. See Note 10 for further information regarding our management agreements with RMR LLC.

RMR Inc. RMR LLC is a majority owned subsidiary of RMR Inc. and RMR Inc. is the managing member of RMR LLC. Adam D. Portnoy, one of our Managing Trustees, is the sole trustee, an officer and the controlling shareholder of ABP Trust, which is the controlling shareholder of RMR Inc., a managing director, president and chief executive officer of RMR Inc., and an officer and employee of RMR LLC. Jennifer B. Clark, our other Managing Trustee, also serves as a managing director and as executive vice president, general counsel and secretary of RMR Inc. and an officer of ABP Trust and RMR LLC. Other officers and employees of RMR LLC also serve as our officers. As of March 31, 2019, we owned 2,637,408 shares of class A common stock of RMR Inc. See Note 5 for further information regarding our investment in RMR Inc.

AIC. We, ABP Trust, Five Star and four other companies to which RMR LLC provides management services currently own AIC in equal amounts. We (including our consolidated joint venture) and the other AIC shareholders participate in a combined property insurance program arranged and reinsured in part by AIC.

As of March 31, 2019 and December 31, 2018, our investment in AIC had a carrying value of $9,102 and $8,632, respectively. These amounts are included in other assets in our condensed consolidated balance sheets. We recognized income related to our investment in AIC, which is presented as equity in earnings of an investee in our condensed consolidated statements of comprehensive income. Our other comprehensive income includes our proportionate part of unrealized gains on securities that are owned by AIC related to our investment in AIC.

For further information about these and other such relationships and certain other related person transactions, refer to our Annual Report.