Consolidated Statements of Equity (Unaudited) (Parenthetical) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Dividends paid or accrued per Common Share of Beneficial Interest	$ 0.1625	$ 0.1625
Dividends paid or accrued per Series D Preferred Share	$ 0.57813
Dividends paid or accrued per Series C Preferred Share		$ 0.40625
Accumulated Distribution in Excess of Net Income
Dividends paid or accrued per Common Share of Beneficial Interest	$ 0.1625	$ 0.1625
Dividends paid or accrued per Series D Preferred Share	$ 0.57813
Dividends paid or accrued per Series C Preferred Share		$ 0.40625