Subsequent Events - Additional Information (Detail) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016 mi	Dec. 31, 2015 USD ($) mi shares MBbls	Dec. 31, 2013 USD ($) shares	Jan. 28, 2016 $ / shares	Dec. 31, 2014 shares
Subsequent Event [Line Items]
Common unitholders, units issued | shares		114,740,148			113,949,868
Subsequent Event [Member]
Subsequent Event [Line Items]
Distribution of dividend | $ / shares				$ 0.78
Distribution payable date	Feb. 12, 2016
Distribution record date	Feb. 08, 2016
Equity Distribution Agreement [Member]
Subsequent Event [Line Items]
Common unitholders, units issued | shares			1,839,430
Proceeds from issuance of common stock			$ 87
Offering costs			$ 1
Offer value of common stock remaining available for sale		$ 349
Panola [Member]
Subsequent Event [Line Items]
Anticipated consideration to be paid for acquisition		$ 26
Pipeline Length In Miles | mi		180
Expected capacity per day | MBbls		100
Aggregate consideration for acquisition		$ 1
Panola [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Pipeline Length In Miles | mi	60