Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Class of Stock [Line Items]
Gross proceeds from sale of shares	$ 0	$ 611,278	$ 621,800
Common shares | Class A common shares
Class of Stock [Line Items]
Issuance of common shares (in shares)			29,610,854
Common shares issued (in dollars per share)			$ 21.00
QIA
Class of Stock [Line Items]
Interest held by QIA (as a percent)			9.90%
QIA | Common shares | Class A common shares
Class of Stock [Line Items]
Interest held by QIA (as a percent)			19.40%