Equity (Details 1) (USD $)	3 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014
7.875% Series A [Member]
Dividends on preferred shares/units
Dividend per Share/Unit	$ 0.49	$ 0.49	$ 0.49	$ 0.49
Record Date	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014
Payable Date	Jan. 15, 2015	Oct. 15, 2014	Jul. 15, 2014	Apr. 15, 2014
8.00% Series B [Member]
Dividends on preferred shares/units
Dividend per Share/Unit	$ 0.50	$ 0.50	$ 0.50	$ 0.50
Record Date	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014
Payable Date	Jan. 15, 2015	Oct. 15, 2014	Jul. 15, 2014	Apr. 15, 2014
6.50% Series C [Member]
Dividends on preferred shares/units
Dividend per Share/Unit	$ 0.41	$ 0.41	$ 0.41	$ 0.41
Record Date	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014
Payable Date	Jan. 15, 2015	Oct. 15, 2014	Jul. 15, 2014	Apr. 15, 2014