Equity Method Investments - Summary of Income Statement Data for Equity Method Investments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	$ 80	$ 48	$ 150	$ 88
Total revenue	121	129	252	229
Operating income	48	57	113	62
Amberjack
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	31	16	63	16
Total Revenues	74	40	155	40
Total Operating Expenses	17	10	36	10
Operating Income	57	30	119	30
Net Income	58	30	120	30
Amberjack | May 2018 Acquisition
Schedule of Equity Method Investments [Line Items]
Total Revenues		70		132
Total Operating Expenses		17		36
Operating Income		53		96
Mars
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	29	21	58	46
Total Revenues	67	52	130	109
Total Operating Expenses	26	22	48	43
Operating Income	41	30	82	66
Net Income	42	30	83	66
Bengal
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	5	6	10	10
Total Revenues	19	18	37	33
Total Operating Expenses	9	7	16	14
Operating Income	10	11	21	19
Net Income	10	11	21	19
Explorer
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	7	0	7	0
Total Revenues	37		37
Total Operating Expenses	13		13
Operating Income	24		24
Net Income	18		18
Explorer | June 2019 Acquisition
Schedule of Equity Method Investments [Line Items]
Total Revenues	133		222
Total Operating Expenses	48		94
Operating Income	85		128
Colonial Pipeline Company (“Colonial”)
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	4	0	4	0
Total Revenues	88		88
Total Operating Expenses	44		44
Operating Income	44		44
Net Income	27		27
Colonial Pipeline Company (“Colonial”) | June 2019 Acquisition
Schedule of Equity Method Investments [Line Items]
Total Revenues	325		696
Total Operating Expenses	164		330
Operating Income	161		366
Poseidon
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	0	0	0	6
Total Revenues	34	27	65	56
Total Operating Expenses	8	8	17	17
Operating Income	26	19	48	39
Net Income	23	17	43	36
Other
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	4	5	8	10
Total Revenues	56	39	86	75
Total Operating Expenses	37	15	55	30
Operating Income	19	24	31	45
Net Income	$ 17	$ 21	$ 26	$ 40