Shareholders' Equity (Summary Of Dividends Declared And Paid Per Share) (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Preferred Stock, Dividend Rate, Percentage	5.417%	5.417%	5.417%	5.417%	5.417%
Common Shares [Member]
Dividend declared, common share			$ 2.030	$ 1.990
Dividend paid, common share			$ 2.010	$ 1.980
5.417% Series 1 Cumulative Convertible Preferred [Member]
Dividend declared, preferred share			$ 1.016	$ 1.016
Dividend paid, preferred share			$ 1.016	$ 1.016