Net Income Per Common Unit - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Apr. 16, 2018	Jan. 31, 2008
Unit Repurchase Program [Line Items]
Amount remaining available for repurchases	$ 335,800,000
Common stock repurchased, units	0	0
Subsequent Event
Unit Repurchase Program [Line Items]
Amount authorized to repurchase under unit repurchase program			$ 1,000,000,000
Blackstone
Unit Repurchase Program [Line Items]
Amount authorized to repurchase under unit repurchase program				$ 500,000,000