Beneficiaries Equity of The Parent Company (DetailsTextuals) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2011	Jun. 30, 2010	Jul. 06, 2011	May 31, 2011	May 02, 2006
Beneficiaries Equity of The Parent Company (Textuals) [Abstract]
Redeemable limited partnership units excluded from the diluted earnings per share computations		9,809,759	2,809,108
Dividend declared per common share					$ 0.15
Amount of dividend declared				$ 20,500,000
Preferential return for series C		7.50%
Preferential return for series D		7.375%
Dividend paid for series C preferred shares	900,000	900,000
Dividend paid for series D preferred shares	1,100,000	1,100,000
Shares authorized for Equity Offering Program		15,000,000
Maximum percentage of Gross sale price per share, compensation to sales agents		2.00%
Issuance of Common Shares of Beneficial Interest, shares		679,285
Average sales price per share		$ 12.18
Issuance of Common Shares of Beneficial Interest		$ 8,272,000	$ 41,692,000
No of shares sold by the company	6,421,553
Remaining shares available for sales	8,578,447
Common partnership units issued to the parent company		679,285
Common shares capacity restored						3,500,000
Additional shares Expected to be purchased under program	500,000	500,000