Shareholders' Equity / Partners' Capital - Class A Common Share Offering (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Class of Stock [Line Items]
Proceeds from issuance of shares/units			$ 694,765	$ 0
Class A common shares/units
Class of Stock [Line Items]
Shares issued during period (in shares)	13,800,000	14,842,982
Common shares, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01		$ 0.01
Proceeds from issuance of shares/units		$ 336,500
Stock issuance costs	$ 9,200	$ 300	$ 10,444	$ 0
Underwritten Public Offering | Class A common shares/units
Class of Stock [Line Items]
Proceeds from issuance of shares/units	$ 312,000