10. Debt

        Our debt consisted of the following (dollars in thousands):

        Effective September 1, 2011, we entered into a credit agreement providing for an unsecured revolving credit facility (the "Revolving Credit Facility") with a group of lenders for which J.P. Morgan Securities LLC and KeyBanc Capital Markets acted as joint lead arrangers and joint book runners, KeyBank National Association acted as administrative agent and JPMorgan Chase Bank, N.A. and Bank of America, N.A. acted as co-syndication agents. The lenders' aggregate commitment under the facility is $1.0 billion, with a right for us to increase the lenders' aggregate commitment to $1.5 billion, provided that there is no default under the facility. Amounts available under the facility are computed based on 60% of our unencumbered asset value, as defined in the agreement. The facility matures on September 1, 2014, and may be extended by one year at our option, provided that there is no default under the facility and we pay an extension fee of 0.20% of the total availability of the facility. The interest rate on the facility is based on LIBOR (customarily the 30-day rate) plus 1.75% to 2.50%, as determined by our leverage levels. The facility also carries a quarterly fee that is based on the unused amount of the facility multiplied by a per annum rate of 0.25% to 0.35%. As of December 31, 2011, the maximum amount of borrowing capacity under this facility totaled $1.0 billion, of which $329.6 million was available.

        Effective September 1, 2011, we entered into an unsecured term loan agreement ("Term Loan Agreement") with the same group of lenders as the Revolving Credit Facility under which we borrowed $400.0 million, with a right for us to borrow an additional $100.0 million, provided that there is no default under the agreement. The Term Loan Agreement matures on September 1, 2015, and may be extended by one year at our option, provided that there is no default and we pay an extension fee of 0.20% of the total availability of the agreement. The variable interest rate on the Term Loan Agreement is based on LIBOR rate (customarily the 30-day rate) plus 1.65% to 2.40%, as determined by our leverage levels.

        Upon entry into the Revolving Credit Facility and Term Loan Agreement on September 1, 2011, we repaid and extinguished our previously existing Revolving Credit Facility and Revolving Construction Facility and used most of the remaining proceeds to repay two variable rate secured loans totaling $270.3 million. Upon the early extinguishment of this debt, we recognized a loss of $1.7 million, representing unamortized issuance costs.

        On April 7, 2010, the Operating Partnership issued a $240.0 million aggregate principal amount of 4.25% Exchangeable Senior Notes due 2030. Interest on the notes is payable on April 15 and October 15 of each year. The notes have an exchange settlement feature that provides that the notes may, under certain circumstances, be exchangeable for cash and, at the Operating Partnership's discretion, our common shares at an exchange rate (subject to adjustment) of 20.8513 shares per one thousand dollar principal amount of the notes (exchange rate is as of December 31, 2011 and is equivalent to an exchange price of $47.96 per common share) (the initial exchange rate of the notes was based on a 20% premium over the closing price on the NYSE on the transaction pricing date). On or after April 20, 2015, the Operating Partnership may redeem the notes in cash in whole or in part. The holders of the notes have the right to require us to repurchase the notes in cash in whole or in part on each of April 15, 2015, April 15, 2020 and April 15, 2025, or in the event of a "fundamental change," as defined under the terms of the notes, for a repurchase price equal to 100% of the principal amount of the notes plus accrued and unpaid interest. The notes are general unsecured senior obligations of the Operating Partnership and rank equally in right of payment with all other senior unsecured indebtedness of the Operating Partnership and are guaranteed by us. The initial liability component of this debt issuance was $221.4 million and the equity component was $18.6 million. The carrying value of these notes included an unamortized discount totaling $12.7 million at December 31, 2011 and $16.2 million at December 31, 2010. The effective interest rate on the liability component, including amortization of the issuance costs, is 6.05%. Because the closing price of our common shares at December 31, 2011 and 2010 was less than the exchange price per common share applicable to these notes, the if-converted value of the notes did not exceed the principal amount. The table below sets forth interest expense recognized on these notes before deductions for amounts capitalized (in thousands):

        Until September 15, 2011, the Operating Partnership had $162.5 million aggregate principal amount of 3.50% Exchangeable Senior Notes due 2026. These notes had an exchange settlement feature that provided that the notes were, under certain circumstances, exchangeable for cash (up to the principal amount of the notes) and, with respect to any excess exchange value, were exchangeable into (at our option) cash, our common shares or a combination of cash and our common shares. On September 15, 2011, we repurchased these notes at 100% of the principal amount of $162.5 million after the holders of such notes surrendered them for repurchase pursuant to the terms of the notes and the related Indenture. The effective interest rate under the notes, including amortization of the issuance costs, was 5.97%. The carrying value of these notes at December 31, 2010 included a principal amount of $162.5 million and an unamortized discount totaling $2.6 million. Because the closing price of our common shares at December 31, 2010 was less than the exchange price per common share applicable to these notes, the if-converted value of the notes did not exceed the principal amount. The table below sets forth interest expense recognized on these notes before deductions for amounts capitalized (in thousands):

        At December 31, 2011, we were in default on a $15.2 million nonrecourse mortgage loan secured by a property with an estimated fair value of approximately $9 million that is included in our Strategic Reallocation Plan.

        Certain of our debt instruments require that we comply with a number of restrictive financial covenants, including maximum leverage ratio, unencumbered leverage ratio, minimum net worth, minimum fixed charge coverage, minimum unencumbered interest coverage ratio, minimum debt service and maximum secured indebtedness ratio. As of December 31, 2011, we were well within the compliance requirements of these financial covenants.

        Our debt matures on the following schedule (in thousands):

        Weighted average borrowings under our Revolving Credit Facilities totaled $482.3 million in 2011 and $337.2 million in 2010. The weighted average interest rate on our Revolving Credit Facilities was 1.65% in 2011 and 1.11% in 2010.

        We capitalized interest costs of $17.4 million in 2011, $16.5 million in 2010 and $15.5 million in 2009.

        The following table sets forth information pertaining to the fair value of our debt (in thousands):