Agreements and Transactions with Affiliates - Balances with Affiliates (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Accounts receivable	$ 72	$ 81
Accounts payable	20	19
DCP Midstream, LLC [Member]
Related Party Transaction [Line Items]
Accounts receivable	72	81
Accounts payable	16	15
Unrealized gains on derivative instruments - current	12	32
Unrealized gains on derivative instruments - long-term	7	9
Unrealized losses on derivative instruments - current	5	18
Unrealized losses on derivative instruments - long-term	0	1
Spectra Energy [Member]
Related Party Transaction [Line Items]
Accounts payable	$ 4	$ 4