Shareholders' Equity - Distributions (Details) - $ / shares	1 Months Ended	3 Months Ended		6 Months Ended
	May 31, 2016	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016
Class A common shares
Class of Stock [Line Items]
Common stock dividend declared (in USD per share)		$ 0.05
Declared distributions (in USD per share)			$ 0.05
Class B common shares
Class of Stock [Line Items]
Declared distributions (in USD per share)		$ 0.05	0.05	$ 0.05
5.0% Series A Participating Preferred Shares
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage				5.00%
Preferred stock dividends declared (in USD per share)			0.3125
5.0% Series B Participating Preferred Shares
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage				5.00%
Preferred stock dividends declared (in USD per share)			0.3125
5.5% Series C Participating Preferred Shares
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage				5.50%
Preferred stock dividends declared (in USD per share)			0.34375
Series D Preferred Shares
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage	6.50%	6.50%		6.50%
Preferred stock dividends declared (in USD per share)		$ 0.17153
Series D Convertible Units
Class of Stock [Line Items]
Declared distributions (in USD per share)		0.035		$ 0.035
Series C Convertible Units
Class of Stock [Line Items]
Declared distributions (in USD per share)		$ 0	$ 0.15113	$ 0
Series D Convertible Units
Class of Stock [Line Items]
Percentage of participation eligibility on distributions			70.00%