Equity (Details 1)	3 Months Ended
	Mar. 31, 2018 $ / shares
6.50% Series C [Member]
Dividends on preferred shares/units
Dividend per Share (usd per share)	$ 0.41
Record Date	Mar. 29, 2018
Payable Date	Apr. 16, 2018
6.375% Series D [Member]
Dividends on preferred shares/units
Dividend per Share (usd per share)	$ 0.40
Record Date	Mar. 29, 2018
Payable Date	Apr. 16, 2018