Investments in Unconsolidated Affiliates - Earnings from Investments in Unconsolidated Affiliates (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	$ 125	$ 117	$ 201	$ 230
DCP Sand Hills Pipeline, LLC
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	70	72	148	140
DCP Southern Hills Pipeline, LLC
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	20	22	40	45
Front Range Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	9	9	20	16
Gulf Coast Express [Member]
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	16	0	32	0
Texas Express Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	5	4	9	9
Mont Belvieu Enterprise Fractionator
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	3	3	6	7
Mont Belvieu 1 Fractionator
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	3	4	6	8
Discovery Producer Services LLC
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	1	3	(60)	3
Other
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated affiliates	$ (2)	$ 0	$ 0	$ 2