Shareholders' Equity / Partners' Capital - Share Repurchase (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Feb. 28, 2018
Class A common shares/units
Class of Stock [Line Items]
Repurchase of shares, authorized amount			$ 300,000,000
Average price per share of Class A common shares (in dollars per share)	$ 19.36
Stock repurchased less commission and fees paid	$ 34,900,000
Remaining repurchase authorization	$ 265,100,000
Class A common shares/units | Common Stock
Class of Stock [Line Items]
Repurchases of Class A common shares (in shares)	1,800,000	0
Preferred Shares/Units
Class of Stock [Line Items]
Repurchase of shares, authorized amount	$ 250,000,000		$ 250,000,000