Indebtedness	9 Months Ended
Sep. 30, 2017
Debt Disclosure [Abstract]
Indebtedness	Indebtedness Our principal debt obligations at September 30, 2017 were: (1) our $458,000 of outstanding borrowings under our $1,000,000 unsecured revolving credit facility; (2) our $400,000 unsecured term loan; and (3) an aggregate outstanding principal amount of $3,200,000 of public issuances of unsecured senior notes. Our $1,000,000 revolving credit facility is available for general business purposes, including acquisitions. The maturity date of our revolving credit facility is July 15, 2018 and, subject to our payment of an extension fee and meeting other conditions, we have the option to extend the stated maturity date of our revolving credit facility by one year to July 15, 2019. We can borrow, repay and reborrow funds available under our revolving credit facility until maturity, and no principal repayment is due until maturity. We are required to pay interest on borrowings under our revolving credit facility at the rate of LIBOR plus a premium, which was 110 basis points as of September 30, 2017. We also pay a facility fee, which was 20 basis points per annum at September 30, 2017, on the total amount of lending commitments under our revolving credit facility. Both the interest rate premium and the facility fee are subject to adjustment based upon changes to our credit ratings. As of September 30, 2017, the annual interest rate for the amount outstanding under our revolving credit facility was 2.34%. The weighted average annual interest rate for borrowings under our revolving credit facility was 2.33% and 2.17% for the three and nine months ended September 30, 2017, respectively, and 1.60% and 1.55% for the three and nine months ended September 30, 2016, respectively. As of September 30, 2017 and November 7, 2017, we had $458,000 and $330,000 outstanding and $542,000 and $670,000 available under our revolving credit facility, respectively. Our revolving credit facility is governed by a credit agreement with a syndicate of institutional lenders, which also governs our term loan. Our $400,000 term loan, which matures on April 15, 2019, is prepayable without penalty at any time. We are required to pay interest on the amounts under our term loan at the rate of LIBOR plus a premium, which was 120 basis points as of September 30, 2017. The interest rate premium is subject to adjustment based on changes to our credit ratings. As of September 30, 2017, the annual interest rate for the amount outstanding under our term loan was 2.44%. The weighted average annual interest rate for borrowings under our term loan was 2.43% and 2.20% for the three and nine months ended September 30, 2017, respectively, and 1.69% and 1.65% for the three and nine months ended September 30, 2016, respectively. Our credit agreement also includes a feature under which maximum aggregate borrowings may be increased up to $2,300,000 on a combined basis in certain circumstances. Our credit agreement and our notes indentures and their supplements provide for acceleration of payment of all amounts outstanding upon the occurrence and continuation of certain events of default, such as, in the case of our credit agreement, a change of control of us, which includes RMR LLC ceasing to act as our business manager. Our credit agreement and our senior notes indentures and their supplements also contain a number of covenants, including covenants that restrict our ability to incur debts or to make distributions under certain circumstances and generally require us to maintain certain financial ratios. We believe we were in compliance with the terms and conditions of our credit agreement and our senior notes indentures and their supplements at September 30, 2017. On January 13, 2017, we issued $600,000 aggregate principal amount of senior notes in public offerings, which included $200,000 principal amount of 4.500% senior notes due 2023 and $400,000 principal amount of 4.950% senior notes due 2027. Net proceeds from these offerings were $593,228 after discounts, premiums and expenses. On March 15, 2017, we repurchased at par plus accrued interest $8,431 of the outstanding principal amount of our 3.80% convertible senior notes due 2027, which were tendered by the holders of these notes for repurchase by us. On April 24, 2017, we redeemed at par plus accrued interest the remaining $47 of the outstanding principal amount of these notes. On October 26, 2017, we issued $400,000 principal amount of 3.950% senior notes due 2028 in a public offering. Net proceeds from this offering were $388,244 after discounts and expenses. On October 29, 2017, we redeemed at par all of our outstanding 6.70% senior notes due 2018 for a redemption price equal to the principal amount of $350,000, plus accrued and unpaid interest.

Indebtedness

Our principal debt obligations at September 30, 2017 were: (1) our $458,000 of outstanding borrowings under our $1,000,000 unsecured revolving credit facility; (2) our $400,000 unsecured term loan; and (3) an aggregate outstanding principal amount of $3,200,000 of public issuances of unsecured senior notes.

Our $1,000,000 revolving credit facility is available for general business purposes, including acquisitions. The maturity date of our revolving credit facility is July 15, 2018 and, subject to our payment of an extension fee and meeting other conditions, we have the option to extend the stated maturity date of our revolving credit facility by one year to July 15, 2019. We can borrow, repay and reborrow funds available under our revolving credit facility until maturity, and no principal repayment is due until maturity. We are required to pay interest on borrowings under our revolving credit facility at the rate of LIBOR plus a premium, which was 110 basis points as of September 30, 2017. We also pay a facility fee, which was 20 basis points per annum at September 30, 2017, on the total amount of lending commitments under our revolving credit facility. Both the interest rate premium and the facility fee are subject to adjustment based upon changes to our credit ratings. As of September 30, 2017, the annual interest rate for the amount outstanding under our revolving credit facility was 2.34%. The weighted average annual interest rate for borrowings under our revolving credit facility was 2.33% and 2.17% for the three and nine months ended September 30, 2017, respectively, and 1.60% and 1.55% for the three and nine months ended September 30, 2016, respectively. As of September 30, 2017 and November 7, 2017, we had $458,000 and $330,000 outstanding and $542,000 and $670,000 available under our revolving credit facility, respectively.

Our revolving credit facility is governed by a credit agreement with a syndicate of institutional lenders, which also governs our term loan. Our $400,000 term loan, which matures on April 15, 2019, is prepayable without penalty at any time. We are required to pay interest on the amounts under our term loan at the rate of LIBOR plus a premium, which was 120 basis points as of September 30, 2017. The interest rate premium is subject to adjustment based on changes to our credit ratings. As of September 30, 2017, the annual interest rate for the amount outstanding under our term loan was 2.44%. The weighted average annual interest rate for borrowings under our term loan was 2.43% and 2.20% for the three and nine months ended September 30, 2017, respectively, and 1.69% and 1.65% for the three and nine months ended September 30, 2016, respectively.

Our credit agreement also includes a feature under which maximum aggregate borrowings may be increased up to $2,300,000 on a combined basis in certain circumstances. Our credit agreement and our notes indentures and their supplements provide for acceleration of payment of all amounts outstanding upon the occurrence and continuation of certain events of default, such as, in the case of our credit agreement, a change of control of us, which includes RMR LLC ceasing to act as our business manager. Our credit agreement and our senior notes indentures and their supplements also contain a number of covenants, including covenants that restrict our ability to incur debts or to make distributions under certain circumstances and generally require us to maintain certain financial ratios. We believe we were in compliance with the terms and conditions of our credit agreement and our senior notes indentures and their supplements at September 30, 2017.

On January 13, 2017, we issued $600,000 aggregate principal amount of senior notes in public offerings, which included $200,000 principal amount of 4.500% senior notes due 2023 and $400,000 principal amount of 4.950% senior notes due 2027. Net proceeds from these offerings were $593,228 after discounts, premiums and expenses.

On March 15, 2017, we repurchased at par plus accrued interest $8,431 of the outstanding principal amount of our 3.80% convertible senior notes due 2027, which were tendered by the holders of these notes for repurchase by us. On April 24, 2017, we redeemed at par plus accrued interest the remaining $47 of the outstanding principal amount of these notes.

On October 26, 2017, we issued $400,000 principal amount of 3.950% senior notes due 2028 in a public offering. Net proceeds from this offering were $388,244 after discounts and expenses.

On October 29, 2017, we redeemed at par all of our outstanding 6.70% senior notes due 2018 for a redemption price equal to the principal amount of $350,000, plus accrued and unpaid interest.