Subsequent Events (Schedule Of Dividends Declared And Distributions Per Unit) (Details) (USD $)	3 Months Ended
	Mar. 31, 2013
Subsequent Event [Line Items]
Dividend and distribution payable date	Mar. 29, 2013
Series E Cumulative Convertible Preferred Units [Member]
Subsequent Event [Line Items]
Annual equivalent rate of dividend and distribution	1.750
Series F Cumulative Convertible Preferred Units [Member]
Subsequent Event [Line Items]
Annual equivalent rate of dividend and distribution	1.656
Subsequent Event [Member] | Series E Cumulative Convertible Preferred Units [Member]
Subsequent Event [Line Items]
Dividend and distribution amount	0.437500
Dividend and distribution payable date	Jun. 28, 2013
Dividend and distribution payable to holders of record on	Jun. 14, 2013
Annual equivalent rate of dividend and distribution	1.750
Subsequent Event [Member] | Series F Cumulative Convertible Preferred Units [Member]
Subsequent Event [Line Items]
Dividend and distribution amount	0.414063
Dividend and distribution payable date	Jun. 28, 2013
Dividend and distribution payable to holders of record on	Jun. 14, 2013
Annual equivalent rate of dividend and distribution	1.656
Subsequent Event [Member] | Series G Cumulative Convertible Preferred Units [Member] [Member]
Subsequent Event [Line Items]
Dividend and distribution amount	0.334550	[1]
Dividend and distribution payable date	Jun. 28, 2013
Dividend and distribution payable to holders of record on	Jun. 14, 2013
Annual equivalent rate of dividend and distribution	1.46875
Subsequent Event [Member] | Common Stock [Member]
Subsequent Event [Line Items]
Dividend and distribution amount	0.780000
Dividend and distribution payable date	Jun. 28, 2013
Dividend and distribution payable to holders of record on	Jun. 14, 2013
Annual equivalent rate of dividend and distribution	3.120

[1] Represents a pro rata dividend from and including the original issue date to and including June 30, 2013.