Shareholders' Equity / Partners' Capital - Share Repurchase (Details) - Class A common shares/units - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Class of Stock [Line Items]
Repurchase of Class A common stock, authorized amount			$ 300,000,000
Average price per share of Class A common shares (in dollars per share)		$ 15.44
Total price from repurchase of common shares		$ 96,000,000
Remaining repurchase authorization	$ 146,700,000
Common Stock
Class of Stock [Line Items]
Repurchases of Class A common shares (in shares)	0	6,200,000