Notes and Bonds Payable	9 Months Ended
Sep. 30, 2013
Debt Disclosure [Abstract]
Notes and Bonds Payable	Notes and Bonds Payable Third Quarter In September 2013, the Company assumed a mortgage note payable of approximately $12.0 million upon acquisition of a real estate property and recorded a fair value premium of approximately $0.7 million. The mortgage note payable has a contractual interest rate of 6.17% (effective rate of 5.25%) and matures in 2027. See Note 2 of the Condensed Consolidated Financial Statements for more information regarding this transaction. Second Quarter In April 2013, the Company redeemed its 5.125% unsecured senior notes due 2014 at a redemption price equal to an aggregate of $277.3 million, consisting of outstanding principal of $264.7 million, accrued interest as of the redemption date of $0.7 million, and a "make-whole" amount of approximately $11.9 million for the early extinguishment of debt. The unaccreted discount on these notes of $0.2 million and deferred financing costs of $0.2 million were written off upon redemption. The Company recognized a loss on early extinguishment of debt of approximately $12.3 million related to this redemption. In June 2013, the Company repaid a $1.1 million mortgage note payable upon disposal of a property in Iowa. In connection with the repayment, the Company incurred a $0.3 million prepayment penalty which has been recorded as a loss on extinguishment of debt in discontinued operations. See Note 2 to the Condensed Consolidated Financial Statements for additional information about this disposition. In June 2013, the Company prepaid in full a secured loan from Teachers Insurance and Annuity Association of America ("TIAA") bearing an interest rate of 7.25% at an amount equal to $94.3 million, consisting of outstanding principal of $77.0 million, accrued interest as of the redemption date of $0.5 million and a prepayment penalty of approximately $16.8 million. The unamortized deferred financing costs on this loan of $0.5 million were written off upon repayment. The Company recognized a loss on early extinguishment of debt of approximately $17.4 million related to this prepayment. First Quarter In February 2013, the Company entered into an amendment that extended the original maturity date of its unsecured credit facility (the "Unsecured Credit Facility") from October 14, 2015 to April 14, 2017. The amendment also provides the Company with two six-month extension options that could extend the maturity date to April 14, 2018. Each option is subject to an extension fee of 0.075% of the aggregate commitments. Amounts outstanding under the Unsecured Credit Facility bear interest at LIBOR plus an applicable margin rate. The margin rate, which depends on the Company's credit ratings, ranges from 0.95% to 1.75% (currently at 1.4%). In addition, the Company pays a facility fee per annum on the aggregate amount of commitments ranging from 0.15% to 0.35% (currently at 0.30%). In connection with the amendment, the Company paid up-front fees to the lenders of approximately $2.7 million, included in Other assets, which is being amortized over the term of the facility. The Company wrote-off certain unamortized deferred financing costs of the original facility of approximately $0.3 million upon execution of the amendment. As of September 30, 2013, the Company had $185.0 million outstanding under the Unsecured Credit Facility and had a remaining borrowing capacity of approximately $515.0 million. In February 2013, the Company repaid in full a mortgage note payable in the amount of $14.9 million bearing interest at a rate of 6.55% per year. In March 2013, the Company issued $250.0 million of unsecured senior notes due 2023 (the "Senior Notes due 2023") that bear interest at 3.75%, payable semi-annually in arrears on April 15 and October 15, commencing October 15, 2013, and mature on April 15, 2023, unless redeemed earlier by the Company. The Senior Notes due 2023 were issued at a discount of approximately $2.1 million, which yielded a 3.85% interest rate per annum upon issuance. The Company incurred $2.1 million in debt issuance costs that are included in Other assets which is being amortized to maturity. The Senior Notes due 2023 have various financial covenant provisions that are required to be met on a quarterly and annual basis. The Company was in compliance with the covenant provisions at September 30, 2013. Senior Note Repurchase Authorization The Company's board of directors has authorized the repurchase of up to $50 million of the Company's outstanding unsecured senior notes due 2017 in open market transactions from time to time. The Company currently has no specific timeframe within which to purchase these notes and has no obligation to repurchase any notes prior to maturity. Subsequent Activities In October 2013, the Company assumed mortgage notes payable of approximately $16.6 million and $11.2 million in a real estate property acquisitions. See Note 2 of the Condensed Consolidated Financial Statements for more information regarding these transactions.

Notes and Bonds Payable

Third Quarter

In September 2013, the Company assumed a mortgage note payable of approximately $12.0 million upon acquisition of a real estate property and recorded a fair value premium of approximately $0.7 million. The mortgage note payable has a contractual interest rate of 6.17% (effective rate of 5.25%) and matures in 2027. See Note 2 of the Condensed Consolidated Financial Statements for more information regarding this transaction.

Second Quarter

In April 2013, the Company redeemed its 5.125% unsecured senior notes due 2014 at a redemption price equal to an aggregate of $277.3 million, consisting of outstanding principal of $264.7 million, accrued interest as of the redemption date of $0.7 million, and a "make-whole" amount of approximately $11.9 million for the early extinguishment of debt. The unaccreted discount on these notes of $0.2 million and deferred financing costs of $0.2 million were written off upon redemption. The Company recognized a loss on early extinguishment of debt of approximately $12.3 million related to this redemption.

In June 2013, the Company repaid a $1.1 million mortgage note payable upon disposal of a property in Iowa. In connection with the repayment, the Company incurred a $0.3 million prepayment penalty which has been recorded as a loss on extinguishment of debt in discontinued operations. See Note 2 to the Condensed Consolidated Financial Statements for additional information about this disposition.

In June 2013, the Company prepaid in full a secured loan from Teachers Insurance and Annuity Association of America ("TIAA") bearing an interest rate of 7.25% at an amount equal to $94.3 million, consisting of outstanding principal of $77.0 million, accrued interest as of the redemption date of $0.5 million and a prepayment penalty of approximately $16.8 million. The unamortized deferred financing costs on this loan of $0.5 million were written off upon repayment. The Company recognized a loss on early extinguishment of debt of approximately $17.4 million related to this prepayment.

First Quarter

In February 2013, the Company entered into an amendment that extended the original maturity date of its unsecured credit facility (the "Unsecured Credit Facility") from October 14, 2015 to April 14, 2017. The amendment also provides the Company with two six-month extension options that could extend the maturity date to April 14, 2018. Each option is subject to an extension fee of 0.075% of the aggregate commitments. Amounts outstanding under the Unsecured Credit Facility bear interest at LIBOR plus an applicable margin rate. The margin rate, which depends on the Company's credit ratings, ranges from 0.95% to 1.75% (currently at 1.4%). In addition, the Company pays a facility fee per annum on the aggregate amount of commitments ranging from 0.15% to 0.35% (currently at 0.30%). In connection with the amendment, the Company paid up-front fees to the lenders of approximately $2.7 million, included in Other assets, which is being amortized over the term of the facility. The Company wrote-off certain unamortized deferred financing costs of the original facility of approximately $0.3 million upon execution of the amendment. As of September 30, 2013, the Company had $185.0 million outstanding under the Unsecured Credit Facility and had a remaining borrowing capacity of approximately $515.0 million.

In February 2013, the Company repaid in full a mortgage note payable in the amount of $14.9 million bearing interest at a rate of 6.55% per year.

In March 2013, the Company issued $250.0 million of unsecured senior notes due 2023 (the "Senior Notes due 2023") that bear interest at 3.75%, payable semi-annually in arrears on April 15 and October 15, commencing October 15, 2013, and mature on April 15, 2023, unless redeemed earlier by the Company. The Senior Notes due 2023 were issued at a discount of approximately $2.1 million, which yielded a 3.85% interest rate per annum upon issuance. The Company incurred $2.1 million in debt issuance costs that are included in Other assets which is being amortized to maturity. The Senior Notes due 2023 have various financial covenant provisions that are required to be met on a quarterly and annual basis. The Company was in compliance with the covenant provisions at September 30, 2013.

Senior Note Repurchase Authorization

The Company's board of directors has authorized the repurchase of up to $50 million of the Company's outstanding unsecured senior notes due 2017 in open market transactions from time to time. The Company currently has no specific timeframe within which to purchase these notes and has no obligation to repurchase any notes prior to maturity.

Subsequent Activities

In October 2013, the Company assumed mortgage notes payable of approximately $16.6 million and $11.2 million in a real estate property acquisitions. See Note 2 of the Condensed Consolidated Financial Statements for more information regarding these transactions.