Inventories - Schedule of Inventories (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Components Of Inventory [Line Items]
Total inventories	$ 37	$ 43
Natural Gas [Member]
Components Of Inventory [Line Items]
Total inventories	23	29
Natural Gas Liquids [Member]
Components Of Inventory [Line Items]
Total inventories	$ 14	$ 14