Indebtedness	3 Months Ended
Mar. 31, 2016
Indebtedness
Indebtedness	Note 7. Indebtedness Our principal debt obligations at March 31, 2016 were: (1) outstanding borrowings under our $750,000 unsecured revolving credit facility; (2) $550,000 aggregate outstanding principal amount of term loans (3) $350,000 of senior unsecured notes; and (4) $28,592 aggregate principal amount of mortgage notes. Our $750,000 unsecured revolving credit facility is available for general business purposes, including acquisitions. The maturity date of our unsecured revolving credit facility is January 31, 2019 and, subject to the payment of an extension fee and meeting other conditions, we have an option to extend the stated maturity date of our unsecured revolving credit facility by one year to January 31, 2020. We can borrow, repay and reborrow funds available under our unsecured revolving credit facility until maturity and no principal repayment is due until maturity. We are required to pay interest at a rate of LIBOR plus a premium, which was 125 basis points per annum at March 31, 2016, on borrowings under our unsecured revolving credit facility. We also pay a facility fee on the total amount of lending commitments under our unsecured revolving credit facility, which was 25 basis points per annum at March 31, 2016. Both the interest rate premium and the facility fee are subject to adjustment based upon changes to our credit ratings. As of March 31, 2016, the annual interest rate payable on borrowings under our unsecured revolving credit facility was 1.6% and the weighted average annual interest rate for borrowings under our unsecured revolving credit facility was 1.6% and 2.0%, respectively, for the three months ended March 31, 2016 and 2015. As of March 31, 2016 and April 26, 2016, we had $311,000 and $303,000 outstanding under our unsecured revolving credit facility, respectively. Our $300,000 unsecured term loan, which matures on March 31, 2020, is prepayable without penalty at any time. We are required to pay interest at a rate of LIBOR plus a premium, which was 140 basis points per annum at March 31, 2016, on the amount outstanding under our $300,000 unsecured term loan. The interest rate premium is subject to adjustment based upon changes to our credit ratings. As of March 31, 2016, the annual interest rate for the amount outstanding under our $300,000 unsecured term loan was 1.8%. The weighted average annual interest rate under our $300,000 unsecured term loan was 1.8% and 1.6%, respectively, for the three months ended March 31, 2016 and 2015. Our $250,000 unsecured term loan, which matures on March 31, 2022, is prepayable at any time. If our $250,000 unsecured term loan is repaid on or prior to November 21, 2016, a prepayment premium of 1.0% of the amount repaid will be payable. Subsequent to November 21, 2016, no prepayment premium will be payable. We are required to pay interest at a rate of LIBOR plus a premium, which was 180 basis points per annum as of March 31, 2016, on the amount outstanding under our $250,000 unsecured term loan. The interest rate premium is subject to adjustment based upon changes to our credit ratings. As of March 31, 2016, the annual interest rate for the amount outstanding under our $250,000 unsecured term loan was 2.2%. The weighted average annual interest rate under our $250,000 unsecured term loan was 2.2% and 2.0%, respectively, for the three months ended March 31, 2016 and 2015. Our $750,000 unsecured revolving credit facility, our $300,000 unsecured term loan and our $250,000 unsecured term loan are governed by a credit agreement with a syndicate of institutional lenders that includes a number of features common to all of these credit arrangements. This credit agreement also includes a feature under which the maximum aggregate borrowing availability may be increased to up to $2,500,000 on a combined basis in certain circumstances. Our $350,000 of 3.75% senior unsecured notes due 2019 are governed by an indenture and a supplement to the indenture, and require semi-annual payments of interest only through maturity. The outstanding amount of these notes may be prepaid at par (plus accrued and unpaid interest) on or after July 15, 2019 or before that date together with a make whole premium. Our credit agreement and 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 credit agreement and our senior unsecured notes indenture and its supplement also contain a number of covenants, including covenants that restrict our ability to incur debts, require us to maintain certain financial ratios and, in the case of our credit agreement, restrict our ability to make distributions under certain circumstances. We believe we were in compliance with the terms and conditions of the respective covenants under our credit agreement and senior unsecured notes indenture and its supplement at March 31, 2016. In February 2016, we repaid, at par, a $23,473 mortgage note requiring annual interest of 6.21% which was secured by one office property (one building) located in Landover, MD. This mortgage note was scheduled to mature in August 2016. We recorded a loss on extinguishment of debt of $21 in the three months ended March 31, 2016, which represented unamortized debt issuance costs related to this note. In March 2016, we repaid, at par, an $83,000 mortgage note requiring annual interest of 5.55% which was secured by one office property (two buildings) located in Reston, VA. This mortgage note was scheduled to mature in April 2016. We recorded a gain on extinguishment of debt of $125 in the three months ended March 31, 2016, which represented the net unamortized debt premium and debt issuance costs related to this note. At March 31, 2016, three of our properties (three buildings) with an aggregate net book value of $54,684 secured three mortgage notes with an aggregate principal amount of $28,592. Our mortgage notes are non-recourse, subject to certain limited exceptions and do not contain any material financial covenants.

Note 7. Indebtedness

Our principal debt obligations at March 31, 2016 were: (1) outstanding borrowings under our $750,000 unsecured revolving credit facility; (2) $550,000 aggregate outstanding principal amount of term loans (3) $350,000 of senior unsecured notes; and (4) $28,592 aggregate principal amount of mortgage notes.

Our $750,000 unsecured revolving credit facility is available for general business purposes, including acquisitions. The maturity date of our unsecured revolving credit facility is January 31, 2019 and, subject to the payment of an extension fee and meeting other conditions, we have an option to extend the stated maturity date of our unsecured revolving credit facility by one year to January 31, 2020. We can borrow, repay and reborrow funds available under our unsecured revolving credit facility until maturity and no principal repayment is due until maturity. We are required to pay interest at a rate of LIBOR plus a premium, which was 125 basis points per annum at March 31, 2016, on borrowings under our unsecured revolving credit facility. We also pay a facility fee on the total amount of lending commitments under our unsecured revolving credit facility, which was 25 basis points per annum at March 31, 2016. Both the interest rate premium and the facility fee are subject to adjustment based upon changes to our credit ratings. As of March 31, 2016, the annual interest rate payable on borrowings under our unsecured revolving credit facility was 1.6% and the weighted average annual interest rate for borrowings under our unsecured revolving credit facility was 1.6% and 2.0%, respectively, for the three months ended March 31, 2016 and 2015. As of March 31, 2016 and April 26, 2016, we had $311,000 and $303,000 outstanding under our unsecured revolving credit facility, respectively.

Our $300,000 unsecured term loan, which matures on March 31, 2020, is prepayable without penalty at any time. We are required to pay interest at a rate of LIBOR plus a premium, which was 140 basis points per annum at March 31, 2016, on the amount outstanding under our $300,000 unsecured term loan. The interest rate premium is subject to adjustment based upon changes to our credit ratings. As of March 31, 2016, the annual interest rate for the amount outstanding under our $300,000 unsecured term loan was 1.8%. The weighted average annual interest rate under our $300,000 unsecured term loan was 1.8% and 1.6%, respectively, for the three months ended March 31, 2016 and 2015.

Our $250,000 unsecured term loan, which matures on March 31, 2022, is prepayable at any time. If our $250,000 unsecured term loan is repaid on or prior to November 21, 2016, a prepayment premium of 1.0% of the amount repaid will be payable. Subsequent to November 21, 2016, no prepayment premium will be payable. We are required to pay interest at a rate of LIBOR plus a premium, which was 180 basis points per annum as of March 31, 2016, on the amount outstanding under our $250,000 unsecured term loan. The interest rate premium is subject to adjustment based upon changes to our credit ratings. As of March 31, 2016, the annual interest rate for the amount outstanding under our $250,000 unsecured term loan was 2.2%. The weighted average annual interest rate under our $250,000 unsecured term loan was 2.2% and 2.0%, respectively, for the three months ended March 31, 2016 and 2015.

Our $750,000 unsecured revolving credit facility, our $300,000 unsecured term loan and our $250,000 unsecured term loan are governed by a credit agreement with a syndicate of institutional lenders that includes a number of features common to all of these credit arrangements. This credit agreement also includes a feature under which the maximum aggregate borrowing availability may be increased to up to $2,500,000 on a combined basis in certain circumstances.

Our $350,000 of 3.75% senior unsecured notes due 2019 are governed by an indenture and a supplement to the indenture, and require semi-annual payments of interest only through maturity. The outstanding amount of these notes may be prepaid at par (plus accrued and unpaid interest) on or after July 15, 2019 or before that date together with a make whole premium.

Our credit agreement and 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 credit agreement and our senior unsecured notes indenture and its supplement also contain a number of covenants, including covenants that restrict our ability to incur debts, require us to maintain certain financial ratios and, in the case of our credit agreement, restrict our ability to make distributions under certain circumstances. We believe we were in compliance with the terms and conditions of the respective covenants under our credit agreement and senior unsecured notes indenture and its supplement at March 31, 2016.

In February 2016, we repaid, at par, a $23,473 mortgage note requiring annual interest of 6.21% which was secured by one office property (one building) located in Landover, MD. This mortgage note was scheduled to mature in August 2016. We recorded a loss on extinguishment of debt of $21 in the three months ended March 31, 2016, which represented unamortized debt issuance costs related to this note.

In March 2016, we repaid, at par, an $83,000 mortgage note requiring annual interest of 5.55% which was secured by one office property (two buildings) located in Reston, VA. This mortgage note was scheduled to mature in April 2016. We recorded a gain on extinguishment of debt of $125 in the three months ended March 31, 2016, which represented the net unamortized debt premium and debt issuance costs related to this note.

At March 31, 2016, three of our properties (three buildings) with an aggregate net book value of $54,684 secured three mortgage notes with an aggregate principal amount of $28,592. Our mortgage notes are non-recourse, subject to certain limited exceptions and do not contain any material financial covenants.