Indebtedness	3 Months Ended
Mar. 31, 2016
Indebtedness
Indebtedness	Note 6. Indebtedness Our principal debt obligations at March 31, 2016 were: (1) our $328,000 of outstanding borrowings under our $750,000 unsecured revolving credit facility; (2) our $350,000 unsecured term loan; (3) an aggregate outstanding principal amount of $1,450,000 of public issuances of senior unsecured notes; and (4) an aggregate outstanding principal amount of $285,433 of mortgage notes. Our $750,000 unsecured revolving credit facility and our $350,000 unsecured term loan are governed by a credit agreement with a syndicate of institutional lenders. This credit agreement includes a feature under which the maximum aggregate borrowing availability under the unsecured revolving credit facility and the unsecured term loan may be increased to up to $2,200,000 on a combined basis under certain circumstances. Our $750,000 unsecured revolving credit facility has a maturity date of March 29, 2019, interest payable on borrowings of LIBOR plus 105 basis points and a facility fee of 20 basis points per annum, based on the total amount of lending commitments. Both the interest rate premium and the facility fee for the unsecured revolving credit facility are subject to adjustment based on changes to our credit ratings. Upon the payment of an extension fee and meeting other conditions, we have the option to extend the maturity date of the unsecured revolving credit facility to March 29, 2020. As of both March 31, 2016 and December 31, 2015, the annual interest rate payable on borrowings under our unsecured revolving credit facility was 1.44%. The weighted average annual interest rate for borrowings under our unsecured revolving credit facility was 1.44% and 1.28% for the three months ended March 31, 2016 and 2015, respectively. We can borrow, repay and reborrow funds available under our unsecured revolving credit facility until maturity, and no principal repayment is due until maturity. As of March 31, 2016 and April 25, 2016, we had $328,000 and $318,000, respectively, outstanding under our unsecured revolving credit facility. Our $350,000 unsecured term loan has a maturity date of March 31, 2020 and interest payable on the amount outstanding of LIBOR plus 115 basis points. The interest rate premium for our unsecured term loan is subject to adjustment based on changes to our credit ratings. As of March 31, 2016 and December 31, 2015, the annual interest rate payable for the amount outstanding under our unsecured term loan was 1.59% and 1.39%, respectively. The weighted average annual interest rate for the amount outstanding under our unsecured term loan was 1.58% and 1.35% for the three months ended March 31, 2016 and 2015, respectively. Our credit agreement and our senior unsecured notes indenture and its supplement provide for acceleration of payment of all amounts due thereunder 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 The RMR Group LLC, or RMR LLC, ceasing to act as our business manager and property manager. Our senior unsecured notes indenture and its supplement and our credit agreement 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 the respective covenants under our senior unsecured notes indenture and its supplement and our credit agreement at March 31, 2016. At March 31, 2016, nine of our properties (12 buildings) with a net book value of $455,388 had secured mortgage notes we assumed in connection with our acquisition of those properties. The aggregate principal amount outstanding under these mortgage notes as of March 31, 2016 was $285,433. These mortgage notes are non-recourse, subject to certain limited exceptions, and do not contain any material financial covenants.

Note 6. Indebtedness

Our principal debt obligations at March 31, 2016 were: (1) our $328,000 of outstanding borrowings under our $750,000 unsecured revolving credit facility; (2) our $350,000 unsecured term loan; (3) an aggregate outstanding principal amount of $1,450,000 of public issuances of senior unsecured notes; and (4) an aggregate outstanding principal amount of $285,433 of mortgage notes.

Our $750,000 unsecured revolving credit facility and our $350,000 unsecured term loan are governed by a credit agreement with a syndicate of institutional lenders. This credit agreement includes a feature under which the maximum aggregate borrowing availability under the unsecured revolving credit facility and the unsecured term loan may be increased to up to $2,200,000 on a combined basis under certain circumstances.

Our $750,000 unsecured revolving credit facility has a maturity date of March 29, 2019, interest payable on borrowings of LIBOR plus 105 basis points and a facility fee of 20 basis points per annum, based on the total amount of lending commitments. Both the interest rate premium and the facility fee for the unsecured revolving credit facility are subject to adjustment based on changes to our credit ratings. Upon the payment of an extension fee and meeting other conditions, we have the option to extend the maturity date of the unsecured revolving credit facility to March 29, 2020. As of both March 31, 2016 and December 31, 2015, the annual interest rate payable on borrowings under our unsecured revolving credit facility was 1.44%. The weighted average annual interest rate for borrowings under our unsecured revolving credit facility was 1.44% and 1.28% for the three months ended March 31, 2016 and 2015, respectively. We can borrow, repay and reborrow funds available under our unsecured revolving credit facility until maturity, and no principal repayment is due until maturity. As of March 31, 2016 and April 25, 2016, we had $328,000 and $318,000, respectively, outstanding under our unsecured revolving credit facility.

Our $350,000 unsecured term loan has a maturity date of March 31, 2020 and interest payable on the amount outstanding of LIBOR plus 115 basis points. The interest rate premium for our unsecured term loan is subject to adjustment based on changes to our credit ratings. As of March 31, 2016 and December 31, 2015, the annual interest rate payable for the amount outstanding under our unsecured term loan was 1.59% and 1.39%, respectively. The weighted average annual interest rate for the amount outstanding under our unsecured term loan was 1.58% and 1.35% for the three months ended March 31, 2016 and 2015, respectively.

Our credit agreement and our senior unsecured notes indenture and its supplement provide for acceleration of payment of all amounts due thereunder 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 The RMR Group LLC, or RMR LLC, ceasing to act as our business manager and property manager. Our senior unsecured notes indenture and its supplement and our credit agreement 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 the respective covenants under our senior unsecured notes indenture and its supplement and our credit agreement at March 31, 2016.

At March 31, 2016, nine of our properties (12 buildings) with a net book value of $455,388 had secured mortgage notes we assumed in connection with our acquisition of those properties. The aggregate principal amount outstanding under these mortgage notes as of March 31, 2016 was $285,433. These mortgage notes are non-recourse, subject to certain limited exceptions, and do not contain any material financial covenants.