Indebtedness	6 Months Ended
Jun. 30, 2016
Indebtedness
Indebtedness	Note 7. Indebtedness Our principal debt obligations at June 30, 2016 were: (1) $550,000 aggregate outstanding principal amount of term loans; (2) an aggregate outstanding principal amount of $660,000 of public issuances of senior unsecured notes; and (3) $28,238 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 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 revolving credit facility by one year to January 31, 2020. 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 at a rate of LIBOR plus a premium, which was 125 basis points per annum at June 30, 2016, on borrowings under our revolving credit facility. We also pay a facility fee on the total amount of lending commitments under our revolving credit facility, which was 25 basis points per annum at June 30, 2016. Both the interest rate premium and the facility fee are subject to adjustment based upon changes to our credit ratings. As of June 30, 2016, the annual interest rate payable on borrowings under our revolving credit facility was 1.7% and the weighted average annual interest rate for borrowings under our revolving credit facility was 1.7% for both the three and six months ended June 30, 2016 and 1.4% and 1.6%, respectively, for the three and six months ended June 30, 2015. As of both June 30, 2016 and July 26, 2016, we had no amounts outstanding under our revolving credit facility. 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 June 30, 2016, on the amount outstanding under our $300,000 term loan. The interest rate premium is subject to adjustment based upon changes to our credit ratings. As of June 30, 2016, the annual interest rate for the amount outstanding under our $300,000 term loan was 1.9%. The weighted average annual interest rate under our $300,000 term loan was 1.8% and 1.6%, respectively, for the three and six months ended June 30, 2016 and 2015. Our $250,000 unsecured term loan, which matures on March 31, 2022, is prepayable at any time. If our $250,000 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 June 30, 2016, on the amount outstanding under our $250,000 term loan. The interest rate premium is subject to adjustment based upon changes to our credit ratings. As of June 30, 2016, the annual interest rate for the amount outstanding under our $250,000 term loan was 2.3%. The weighted average annual interest rate under our $250,000 term loan was 2.2% and 2.0%, respectively, for the three and six months ended June 30, 2016 and 2015. Our $750,000 revolving credit facility, our $300,000 term loan and our $250,000 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. In May 2016, we issued $300,000 of 5.875% senior unsecured notes due 2046 in an underwritten public offering. In June 2016, the underwriters exercised an option to purchase an additional $10,000 of these notes. The net proceeds from this offering of $299,892, after offering expenses, were used to repay all amounts then outstanding under our revolving credit facility and for general business purposes. These notes require quarterly payments of interest only through maturity and may be repaid at par (plus accrued and unpaid interest) on or after May 26, 2021. Our $350,000 of 3.75% senior unsecured notes due 2019 require semi-annual payments of interest only through maturity and may be repaid at par (plus accured and unpaid interest) on or after July 15, 2019 or before that date together with a make whole premium. Both issuances of our senior notes are governed by an indenture and its supplements. Our credit agreement and senior notes indenture and its supplements 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 notes indenture and its supplements 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 notes indenture and its supplements at June 30, 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 six months ended June 30, 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 six months ended June 30, 2016, which represented the net unamortized debt premium and debt issuance costs related to this note. At June 30, 2016, three of our properties (three buildings) with an aggregate net book value of $53,927 secured three mortgage notes with an aggregate principal amount of $28,238. 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 June 30, 2016 were: (1) $550,000 aggregate outstanding principal amount of term loans; (2) an aggregate outstanding principal amount of $660,000 of public issuances of senior unsecured notes; and (3) $28,238 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 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 revolving credit facility by one year to January 31, 2020. 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 at a rate of LIBOR plus a premium, which was 125 basis points per annum at June 30, 2016, on borrowings under our revolving credit facility. We also pay a facility fee on the total amount of lending commitments under our revolving credit facility, which was 25 basis points per annum at June 30, 2016. Both the interest rate premium and the facility fee are subject to adjustment based upon changes to our credit ratings. As of June 30, 2016, the annual interest rate payable on borrowings under our revolving credit facility was 1.7% and the weighted average annual interest rate for borrowings under our revolving credit facility was 1.7% for both the three and six months ended June 30, 2016 and 1.4% and 1.6%, respectively, for the three and six months ended June 30, 2015. As of both June 30, 2016 and July 26, 2016, we had no amounts outstanding under our revolving credit facility.

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 June 30, 2016, on the amount outstanding under our $300,000 term loan. The interest rate premium is subject to adjustment based upon changes to our credit ratings. As of June 30, 2016, the annual interest rate for the amount outstanding under our $300,000 term loan was 1.9%. The weighted average annual interest rate under our $300,000 term loan was 1.8% and 1.6%, respectively, for the three and six months ended June 30, 2016 and 2015.

Our $250,000 unsecured term loan, which matures on March 31, 2022, is prepayable at any time. If our $250,000 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 June 30, 2016, on the amount outstanding under our $250,000 term loan. The interest rate premium is subject to adjustment based upon changes to our credit ratings. As of June 30, 2016, the annual interest rate for the amount outstanding under our $250,000 term loan was 2.3%. The weighted average annual interest rate under our $250,000 term loan was 2.2% and 2.0%, respectively, for the three and six months ended June 30, 2016 and 2015.

Our $750,000 revolving credit facility, our $300,000 term loan and our $250,000 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.

In May 2016, we issued $300,000 of 5.875% senior unsecured notes due 2046 in an underwritten public offering. In June 2016, the underwriters exercised an option to purchase an additional $10,000 of these notes. The net proceeds from this offering of $299,892, after offering expenses, were used to repay all amounts then outstanding under our revolving credit facility and for general business purposes. These notes require quarterly payments of interest only through maturity and may be repaid at par (plus accrued and unpaid interest) on or after May 26, 2021. Our $350,000 of 3.75% senior unsecured notes due 2019 require semi-annual payments of interest only through maturity and may be repaid at par (plus accured and unpaid interest) on or after July 15, 2019 or before that date together with a make whole premium. Both issuances of our senior notes are governed by an indenture and its supplements.

Our credit agreement and senior notes indenture and its supplements 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 notes indenture and its supplements 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 notes indenture and its supplements at June 30, 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 six months ended June 30, 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 six months ended June 30, 2016, which represented the net unamortized debt premium and debt issuance costs related to this note.

At June 30, 2016, three of our properties (three buildings) with an aggregate net book value of $53,927 secured three mortgage notes with an aggregate principal amount of $28,238. Our mortgage notes are non-recourse, subject to certain limited exceptions and do not contain any material financial covenants.