Equity (Details 1) (USD $)	3 Months Ended
	Mar. 31, 2013
7.875% Series A [Member]
Dividends on preferred shares/units
Dividend per Share/Unit	$ 0.49
Record Date	Apr. 01, 2013
Payable Date	Apr. 15, 2013
8.00% Series B [Member]
Dividends on preferred shares/units
Dividend per Share/Unit	$ 0.50
Record Date	Apr. 01, 2013
Payable Date	Apr. 15, 2013
6.50% Series C [Member]
Dividends on preferred shares/units
Dividend per Share/Unit	$ 0.12
Record Date	Apr. 01, 2013
Payable Date	Apr. 15, 2013