Equity Method Investments - Summary of Income Statement Data for Equity Method Investments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	$ 115	$ 73	$ 265	$ 161
Total revenue	125	153	377	382
Operating income	49	78	162	140
Amberjack
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	31	33	94	49
Total Revenues	80	83	235	123
Total Operating Expenses	18	18	54	28
Operating Income	62	65	181	95
Net Income	62	65	182	95
Amberjack | May 2018 Acquisition
Schedule of Equity Method Investments [Line Items]
Total Revenues				214
Total Operating Expenses				54
Operating Income				160
Mars
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	35	30	93	76
Total Revenues	82	69	212	178
Total Operating Expenses	32	26	80	69
Operating Income	50	43	132	109
Net Income	50	43	133	109
Bengal
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	8	5	18	15
Total Revenues	22	18	59	51
Total Operating Expenses	7	7	23	21
Operating Income	15	11	36	30
Net Income	15	11	36	30
Explorer
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	20	0	27	0
Total Revenues	122		159
Total Operating Expenses	51		64
Operating Income	71		95
Net Income	55		73
Explorer | June 2019 Acquisition
Schedule of Equity Method Investments [Line Items]
Total Revenues			344
Total Operating Expenses			145
Operating Income			199
Colonial Pipeline Company (“Colonial”)
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	17	0	21	0
Total Revenues	354		442
Total Operating Expenses	190		234
Operating Income	164		208
Net Income	109		136
Colonial Pipeline Company (“Colonial”) | June 2019 Acquisition
Schedule of Equity Method Investments [Line Items]
Total Revenues			1,050
Total Operating Expenses			520
Operating Income			530
Poseidon
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	0	0	0	6
Total Revenues	31	28	96	84
Total Operating Expenses	9	10	26	27
Operating Income	22	18	70	57
Net Income	20	16	63	52
Other
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	4	5	12	15
Total Revenues	44	37	130	112
Total Operating Expenses	21	18	76	48
Operating Income	23	19	54	64
Net Income	$ 21	$ 17	$ 47	$ 57