Related Person Transactions	9 Months Ended
Sep. 30, 2018
Related Party Transactions [Abstract]
Related Person Transactions	Related Person Transactions We have relationships and historical and continuing transactions with RMR LLC, RMR Inc., SIR, AIC and others related to them, including other companies to which RMR LLC or its subsidiaries provide management services and which have trustees, directors and officers who are also our Trustees or officers. 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. We lease office space to RMR LLC in certain of our properties for RMR LLC's property management offices. We recognized rental income from RMR LLC for leased office space of $263 and $90 for the three months ended September 30, 2018 and 2017, respectively, and $763 and $272 for the nine months ended September 30, 2018 and 2017, respectively. Our office space leases with RMR LLC are terminable by RMR LLC if our management agreements with RMR LLC are terminated. We have historically granted share awards to our officers and other RMR LLC employees under our equity compensation plans. In September 2018 and 2017, we granted annual awards of 58,700 and 57,350 of our common shares, respectively, to our officers and other employees of RMR LLC. In September 2018 and 2017, we purchased 18,875 and 13,636 of our common shares, respectively, valued at the closing price of our common shares on Nasdaq on the applicable date of purchase, in satisfaction of tax withholding and payment obligations in connection with the vesting of awards of our common shares to our officers and other employees of RMR LLC. We include amounts recognized as expense for share awards to RMR LLC employees in general and administrative expenses in our condensed consolidated statements of comprehensive income. 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 of RMR LLC. Mark L. Kleifges, our other Managing Trustee and our Chief Financial Officer and Treasurer, and David M. Blackman, our President and Chief Executive Officer, also serve as executive officers of RMR LLC. Mr. Kleifges has announced his retirement from his position with us, effective December 31, 2018, and Mr. Blackman has been elected to be our other Managing Trustee, effective January 1, 2019. RMR LLC provides management services to us. As of September 30, 2018, we owned 1,214,225 shares of class A common stock of RMR Inc. See Note 8 for further information regarding our investment in RMR Inc. SIR. As of September 30, 2018, we owned 24,918,421 SIR common shares, or approximately 27.8% of its outstanding common shares. As described further in Note 1, on September 14, 2018, we and SIR entered into the Merger Agreement, and on October 9, 2018, we completed the Secondary Sale. Adam D. Portnoy, one of our Managing Trustees, also serves as a managing trustee of SIR, and our President and Chief Executive Officer also serves as a managing trustee and the president and chief executive officer of SIR. RMR LLC provides management services to SIR and us. See Note 1 for further information regarding the Merger Agreement and the Secondary Sale and Notes 12 and 13 for further information regarding our investment in SIR. AIC. We, ABP Trust, SIR and four other companies to which RMR LLC provides management services currently own AIC in equal amounts. We and the other AIC shareholders participate in a combined property insurance program arranged and reinsured in part by AIC. We paid aggregate annual premiums, including taxes and fees, of approximately $1,211 in connection with the renewal of this insurance program for the policy year ending June 30, 2019, which amount may be adjusted from time to time as we acquire and dispose of properties that are included in this insurance program. As of September 30, 2018 and December 31, 2017, our investment in AIC had a carrying value of $9,276 and $8,304, 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 investees 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 RMR LLC, RMR Inc., SIR, AIC and others related to them, including other companies to which RMR LLC or its subsidiaries provide management services and which have trustees, directors and officers who are also our Trustees or officers.

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.

We lease office space to RMR LLC in certain of our properties for RMR LLC's property management offices. We recognized rental income from RMR LLC for leased office space of $263 and $90 for the three months ended September 30, 2018 and 2017, respectively, and $763 and $272 for the nine months ended September 30, 2018 and 2017, respectively. Our office space leases with RMR LLC are terminable by RMR LLC if our management agreements with RMR LLC are terminated.

We have historically granted share awards to our officers and other RMR LLC employees under our equity compensation plans. In September 2018 and 2017, we granted annual awards of 58,700 and 57,350 of our common shares, respectively, to our officers and other employees of RMR LLC. In September 2018 and 2017, we purchased 18,875 and 13,636 of our common shares, respectively, valued at the closing price of our common shares on Nasdaq on the applicable date of purchase, in satisfaction of tax withholding and payment obligations in connection with the vesting of awards of our common shares to our officers and other employees of RMR LLC. We include amounts recognized as expense for share awards to RMR LLC employees in general and administrative expenses in our condensed consolidated statements of comprehensive income.

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 of RMR LLC. Mark L. Kleifges, our other Managing Trustee and our Chief Financial Officer and Treasurer, and David M. Blackman, our President and Chief Executive Officer, also serve as executive officers of RMR LLC. Mr. Kleifges has announced his retirement from his position with us, effective December 31, 2018, and Mr. Blackman has been elected to be our other Managing Trustee, effective January 1, 2019. RMR LLC provides management services to us. As of September 30, 2018, we owned 1,214,225 shares of class A common stock of RMR Inc. See Note 8 for further information regarding our investment in RMR Inc.

SIR. As of September 30, 2018, we owned 24,918,421 SIR common shares, or approximately 27.8% of its outstanding common shares. As described further in Note 1, on September 14, 2018, we and SIR entered into the Merger Agreement, and on October 9, 2018, we completed the Secondary Sale. Adam D. Portnoy, one of our Managing Trustees, also serves as a managing trustee of SIR, and our President and Chief Executive Officer also serves as a managing trustee and the president and chief executive officer of SIR. RMR LLC provides management services to SIR and us. See Note 1 for further information regarding the Merger Agreement and the Secondary Sale and Notes 12 and 13 for further information regarding our investment in SIR.

AIC. We, ABP Trust, SIR and four other companies to which RMR LLC provides management services currently own AIC in equal amounts. We and the other AIC shareholders participate in a combined property insurance program arranged and reinsured in part by AIC. We paid aggregate annual premiums, including taxes and fees, of approximately $1,211 in connection with the renewal of this insurance program for the policy year ending June 30, 2019, which amount may be adjusted from time to time as we acquire and dispose of properties that are included in this insurance program.

As of September 30, 2018 and December 31, 2017, our investment in AIC had a carrying value of $9,276 and $8,304, 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 investees 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.