Shareholders' Equity / Partners' Capital - At the Market Common Share Offering Program (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Proceeds from issuance of class A common shares			$ 0	$ 0	$ 694,765
Class A common shares/units
Class of Stock [Line Items]
Common stock, shares issued (in shares)	13,800,000	14,842,982
Proceeds from issuance of class A common shares	$ 312,000	$ 336,500
Stock issuance costs	9,200	$ 400	$ 0	$ 0	$ 10,637
At the Market - Common Share Offering Program | Class A common shares/units
Class of Stock [Line Items]
Shares reserved for future issuance						$ 400,000
Common stock, shares issued (in shares)			0		2,000,000.0
Proceeds from issuance of class A common shares					$ 46,200
Sale of stock, price per share (in dollars per share)					$ 22.74
Proceeds from sale of stock, net of issuance costs					$ 45,600
Stock issuance costs					$ 600
Capital shares amount authorized for future issuance	$ 500,000
Remaining available for future shares			$ 500,000