Condensed Consolidated Statements Of Equity (Parenthetical) (USD $)	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Common dividend per share	$ 0.55	$ 0.52
6.75% Series D Preferred Shares [Member]
Preferred dividend per share	$ 25.31	$ 25.31
6.95% Series E Preferred Shares [Member]
Preferred dividend per share	$ 86.88	$ 86.88
6.5% Series F Preferred Shares [Member]
Preferred dividend per share	$ 81.25	$ 81.25