Investments in Unconsolidated Affiliates - Earnings from Investments in Unconsolidated Affiliates (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	$ 130	$ 114	$ 331	$ 344
DCP Sand Hills Pipeline, LLC
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	73	72	221	212
DCP Southern Hills Pipeline, LLC
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	19	17	59	62
Front Range Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	9	7	29	23
Gulf Coast Express [Member]
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	17	8	49	8
Texas Express Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	4	3	13	12
Cheyenne Connector
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	3	0	3	0
Mont Belvieu Enterprise Fractionator
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	4	3	10	10
Mont Belvieu 1 Fractionator
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	3	3	9	11
Discovery Producer Services LLC
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	(3)	1	(63)	4
Other
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	$ 1	$ 0	$ 1	$ 2