Indebtedness	3 Months Ended
Mar. 31, 2014
Indebtedness
Indebtedness	Note 5. Indebtedness Our principal debt obligations at March 31, 2014 were: (1) outstanding borrowings under our $750,000 unsecured revolving credit facility; (2) four public issuances of unsecured senior notes, including: (a) $250,000 principal amount at an annual interest rate of 4.30% due 2016, (b) $200,000 principal amount at an annual interest rate of 6.75% due 2020, (c) $300,000 principal amount at an annual interest rate of 6.75% due 2021 and (d) $350,000 principal amount at an annual interest rate of 5.625% due 2042; and (3) $678,514 aggregate principal amount of mortgages secured by 48 of our properties (51 buildings) with maturity dates from 2014 to 2043. The 48 mortgaged properties (51 buildings) had a carrying value of $941,064 at March 31, 2014. We also had two properties subject to capital leases totaling $13,181 at March 31, 2014; these two properties had a carrying value of $18,534 at March 31, 2014. In September 2013, we amended the agreement governing our unsecured revolving credit facility with Wells Fargo Bank, National Association, as administrative agent, and a syndicate of other lenders. As a result of the amendment the stated maturity date of the revolving credit facility was extended from June 24, 2015 to January 15, 2018. Subject to the payment of an extension fee and meeting certain other conditions, we have an option to further extend the stated maturity date by an additional one year. The revolving credit facility agreement provides that we can borrow, repay and reborrow funds available under the revolving credit facility agreement until maturity, and no principal repayment is due until maturity. The $750,000 maximum amount of our revolving credit facility remained unchanged by the amendment. The revolving credit facility agreement continues to include a feature under which maximum borrowings under the facility may be increased to up to $1,500,000 in certain circumstances. Under this amendment, the interest rate paid on borrowings under the revolving credit facility agreement is LIBOR plus a premium of 130 basis points, and the facility fee is 30 basis points per annum on the total amount of lending commitments. Both the interest rate premium and the facility fee are subject to adjustment based upon changes to our credit ratings. The weighted average interest rate for borrowings under our revolving credit facility was 1.42% for the three months ended March 31, 2014. We incurred interest expense and other associated costs related to our revolving credit facility of $425 for the three months ended March 31, 2014. As of March 31, 2014 and May 2, 2014, we had $145,000 and $0 outstanding and $605,000 and $750,000 available under our revolving credit facility, respectively. Our revolving credit facility agreement provides for acceleration of payment of all amounts outstanding upon the occurrence and continuation of certain events of default, such as a change of control of us, which includes Reit Management & Research LLC, or RMR, ceasing to act as our business manager and property manager. Our public debt indentures and related supplements and our credit facility agreement contain a number of financial and other covenants, including covenants that restrict our ability to incur indebtedness or to make distributions under certain circumstances and require us to maintain financial ratios and a minimum net worth. In April 2014, we sold $400,000 of 3.25% senior unsecured notes due 2019 and $250,000 of 4.75% senior unsecured notes due 2024, raising net proceeds of approximately $644,889, after underwriting discounts but before expenses. We plan to use the net proceeds of this offering for general business purposes, including funding the pending acquisition described in Note 3.

Note 5. Indebtedness

Our principal debt obligations at March 31, 2014 were: (1) outstanding borrowings under our $750,000 unsecured revolving credit facility; (2) four public issuances of unsecured senior notes, including: (a) $250,000 principal amount at an annual interest rate of 4.30% due 2016, (b) $200,000 principal amount at an annual interest rate of 6.75% due 2020, (c) $300,000 principal amount at an annual interest rate of 6.75% due 2021 and (d) $350,000 principal amount at an annual interest rate of 5.625% due 2042; and (3) $678,514 aggregate principal amount of mortgages secured by 48 of our properties (51 buildings) with maturity dates from 2014 to 2043. The 48 mortgaged properties (51 buildings) had a carrying value of $941,064 at March 31, 2014. We also had two properties subject to capital leases totaling $13,181 at March 31, 2014; these two properties had a carrying value of $18,534 at March 31, 2014.

In September 2013, we amended the agreement governing our unsecured revolving credit facility with Wells Fargo Bank, National Association, as administrative agent, and a syndicate of other lenders. As a result of the amendment the stated maturity date of the revolving credit facility was extended from June 24, 2015 to January 15, 2018. Subject to the payment of an extension fee and meeting certain other conditions, we have an option to further extend the stated maturity date by an additional one year. The revolving credit facility agreement provides that we can borrow, repay and reborrow funds available under the revolving credit facility agreement until maturity, and no principal repayment is due until maturity. The $750,000 maximum amount of our revolving credit facility remained unchanged by the amendment. The revolving credit facility agreement continues to include a feature under which maximum borrowings under the facility may be increased to up to $1,500,000 in certain circumstances. Under this amendment, the interest rate paid on borrowings under the revolving credit facility agreement is LIBOR plus a premium of 130 basis points, and the facility fee is 30 basis points per annum on the total amount of lending commitments. Both the interest rate premium and the facility fee are subject to adjustment based upon changes to our credit ratings. The weighted average interest rate for borrowings under our revolving credit facility was 1.42% for the three months ended March 31, 2014. We incurred interest expense and other associated costs related to our revolving credit facility of $425 for the three months ended March 31, 2014. As of March 31, 2014 and May 2, 2014, we had $145,000 and $0 outstanding and $605,000 and $750,000 available under our revolving credit facility, respectively.

Our revolving credit facility agreement provides for acceleration of payment of all amounts outstanding upon the occurrence and continuation of certain events of default, such as a change of control of us, which includes Reit Management & Research LLC, or RMR, ceasing to act as our business manager and property manager.

Our public debt indentures and related supplements and our credit facility agreement contain a number of financial and other covenants, including covenants that restrict our ability to incur indebtedness or to make distributions under certain circumstances and require us to maintain financial ratios and a minimum net worth.

In April 2014, we sold $400,000 of 3.25% senior unsecured notes due 2019 and $250,000 of 4.75% senior unsecured notes due 2024, raising net proceeds of approximately $644,889, after underwriting discounts but before expenses. We plan to use the net proceeds of this offering for general business purposes, including funding the pending acquisition described in Note 3.