Equity (Details 1) - $ / shares	3 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015
7.875% Series A [Member]
Dividends on preferred shares/units
Dividend per Share (usd per share)	$ 0.49	$ 0.49	$ 0.49	$ 0.49
Record Date	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015
Payable Date	Jan. 15, 2016	Oct. 15, 2015	Jul. 15, 2015	Apr. 15, 2015
8.00% Series B [Member]
Dividends on preferred shares/units
Dividend per Share (usd per share)	$ 0.50	$ 0.50	$ 0.50	$ 0.50
Record Date	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015
Payable Date	Jan. 15, 2016	Oct. 15, 2015	Jul. 15, 2015	Apr. 15, 2015
6.50% Series C [Member]
Dividends on preferred shares/units
Dividend per Share (usd per share)	$ 0.41	$ 0.41	$ 0.41	$ 0.41
Record Date	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015
Payable Date	Jan. 15, 2016	Oct. 15, 2015	Jul. 15, 2015	Apr. 15, 2015