Preferred Shares Of Beneficial Interest	12 Months Ended
Dec. 31, 2012
Class of Stock Disclosures [Abstract]
Preferred Shares Of Beneficial Interest	Preferred Shares of Beneficial Interest We issued $150 million and $200 million of depositary shares on June 6, 2008 and January 30, 2007, respectively. Each depositary share represents one-hundredth of a Series F Cumulative Redeemable Preferred Share. The depositary shares are redeemable at our option, in whole or in part, for cash at a redemption price of $25 per depositary share, plus any accrued and unpaid dividends thereon. The depositary shares are not convertible or exchangeable for any of our other property or securities. The Series F Preferred Shares pay a 6.5% annual dividend and have a liquidation value of $2,500 per share. The Series F Preferred Shares issued in June 2008 were issued at a discount, resulting in an effective rate of 8.25%. In July 2004, we issued $72.5 million of depositary shares with each share representing one-hundredth of a Series E Cumulative Redeemable Preferred Share. The depositary shares were redeemed on November 21, 2012, at our option, for cash at a redemption price of $25 per depositary share or $72.5 million, plus accrued and unpaid dividends thereon. Upon the redemption of these shares, the related original issuance costs of $2.5 million were reported as a deduction in arriving at net income (loss) attributable to common shareholders. The Series E Preferred Shares paid a 6.95% annual dividend, had a liquidation value of $2,500 per share and were not convertible or exchangeable for any of our property or securities. In April 2003, we issued $75 million of depositary shares with each share representing one-thirtieth of a Series D Cumulative Redeemable Preferred Share. The depositary shares are redeemable at our option, in whole or in part, for cash at a redemption price of $25 per depositary share, plus any accrued and unpaid dividends thereon. The depositary shares are not convertible or exchangeable for any of our property or securities. The Series D Preferred Shares pay a 6.75% annual dividend and have a liquidation value of $750 per share. On February 14, 2013, we called our 6.75% Series D Cumulative Redeemable Preferred Shares with a redemption value of $75.0 million, which will settle on March 18, 2013. As part of our evaluation of our capital plan, we may consider redeeming the Series F Preferred Shares.

Preferred Shares of Beneficial Interest

We issued $150 million and $200 million of depositary shares on June 6, 2008 and January 30, 2007, respectively. Each depositary share represents one-hundredth of a Series F Cumulative Redeemable Preferred Share. The depositary shares are redeemable at our option, in whole or in part, for cash at a redemption price of $25 per depositary share, plus any accrued and unpaid dividends thereon. The depositary shares are not convertible or exchangeable for any of our other property or securities. The Series F Preferred Shares pay a 6.5% annual dividend and have a liquidation value of $2,500 per share. The Series F Preferred Shares issued in June 2008 were issued at a discount, resulting in an effective rate of 8.25%.

In July 2004, we issued $72.5 million of depositary shares with each share representing one-hundredth of a Series E Cumulative Redeemable Preferred Share. The depositary shares were redeemed on November 21, 2012, at our option, for cash at a redemption price of $25 per depositary share or $72.5 million, plus accrued and unpaid dividends thereon. Upon the redemption of these shares, the related original issuance costs of $2.5 million were reported as a deduction in arriving at net income (loss) attributable to common shareholders. The Series E Preferred Shares paid a 6.95% annual dividend, had a liquidation value of $2,500 per share and were not convertible or exchangeable for any of our property or securities.

In April 2003, we issued $75 million of depositary shares with each share representing one-thirtieth of a Series D Cumulative Redeemable Preferred Share. The depositary shares are redeemable at our option, in whole or in part, for cash at a redemption price of $25 per depositary share, plus any accrued and unpaid dividends thereon. The depositary shares are not convertible or exchangeable for any of our property or securities. The Series D Preferred Shares pay a 6.75% annual dividend and have a liquidation value of $750 per share.

On February 14, 2013, we called our 6.75% Series D Cumulative Redeemable Preferred Shares with a redemption value of $75.0 million, which will settle on March 18, 2013.

As part of our evaluation of our capital plan, we may consider redeeming the Series F Preferred Shares.