Shareholders' Equity / Partners' Capital - Participating Preferred Shares (Details) $ / shares in Units, $ in Millions		3 Months Ended			9 Months Ended
	Oct. 03, 2017 market $ / shares shares	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($) $ / shares shares	Sep. 30, 2016	Sep. 30, 2017 USD ($) market $ / shares shares	Mar. 31, 2017 $ / shares	Dec. 31, 2016 $ / shares shares
Class of Stock [Line Items]
Cumulative change in value of index based on purchase prices					50.00%
Number of top markets used for purchase price index | market					20
Liquidation preference value | $			$ 490.7		$ 490.7
Preferred shares, shares outstanding (in shares)			47,810,000		47,810,000		37,010,000
Subsequent Event
Class of Stock [Line Items]
Issuance of common shares, net of offering costs (in shares)	12,398,276
Class A conversion ratio	1.3106
5.0% Series A Participating Preferred Shares
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage			5.00%	5.00%	5.00%
5.0% Series A Participating Preferred Shares | Subsequent Event
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage	5.00%
Preferred shares, shares outstanding (in shares)	5,060,000
5.0% Series B Participating Preferred Shares
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage			5.00%	5.00%	5.00%
5.0% Series B Participating Preferred Shares | Subsequent Event
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage	5.00%
Preferred shares, shares outstanding (in shares)	4,400,000
5.5% Series C Participating Preferred Shares
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage			5.50%	5.50%	5.50%
Class A common shares/units
Class of Stock [Line Items]
Common shares, par value (in dollars per share) | $ / shares			$ 0.01		$ 0.01	$ 0.01	$ 0.01
Class A common shares/units | Scenario, Forecast
Class of Stock [Line Items]
Allocation to participating preferred shareholders | $		$ 27.6
Class A common shares/units | Subsequent Event
Class of Stock [Line Items]
Common shares, par value (in dollars per share) | $ / shares	$ 0.01
Percent of liquidation preference	50.00%
Number of markets used in calculation of conversion ratio | market	20