Subsequent Events - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		6 Months Ended
	Aug. 02, 2017	Aug. 04, 2017	Feb. 29, 2016	Jun. 30, 2017	Jun. 30, 2016
Subsequent Event [Line Items]
Proceeds from sale of common stock				$ 189,757	$ 740,025
Subsequent Event | Dividend Declared
Subsequent Event [Line Items]
Distributions declared per common unit (in dollars per unit)	$ 0.44
Common shares
Subsequent Event [Line Items]
Net proceeds from sale of common stock (in shares)			17,940,000	3,925,456
Shares issued as a result of ACC equity offering (in dollars per share)			$ 41.25
Proceeds from sale of common stock			$ 740,000
Common shares | Subsequent Event
Subsequent Event [Line Items]
Net proceeds from sale of common stock (in shares)		0
Shares issued as a result of ACC equity offering (in dollars per share)		$ 48.09
Proceeds from sale of common stock		$ 1,100