Consolidated Statements of Equity - USD ($) $ in Millions	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Non-controlling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of new accounting principle in period of adoption	$ 64				$ 63		$ 1
Beginning balance at Dec. 31, 2017	20,828	$ 7	$ (9,869)	$ 11,262	12,864	$ (231)	6,795
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	219				37		182
Dividends declared on common stock	(219)				(219)
Distributions to noncontrolling interests	(179)						(179)
Contributions from noncontrolling interests	1						1
Other comprehensive loss	(2)					(2)
Shares repurchased	(1,327)		(1,327)
Shares returned - stock based compensation			(4)
Shares issued - stock based compensation				27
Net shares issued - stock based compensation	24						1
Impact from equity transactions of MPLX & ANDX	(546)			2,380			(2,926)
Ending balance at Mar. 31, 2018	18,863	7	(11,200)	13,669	12,745	(233)	3,875
Beginning balance at Dec. 31, 2017	20,828	7	(9,869)	11,262	12,864	(231)	6,795
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive loss	(2)
Impact from equity transactions of MPLX & ANDX				2,381
Ending balance at Jun. 30, 2018	18,818	7	(12,093)	13,688	13,589	(233)	3,860
Beginning balance at Mar. 31, 2018	18,863	7	(11,200)	13,669	12,745	(233)	3,875
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	1,215				1,055		160
Dividends declared on common stock	(211)				(211)
Distributions to noncontrolling interests	(182)						(182)
Contributions from noncontrolling interests	4						4
Other comprehensive loss	0					0
Shares repurchased	(885)		(885)
Shares returned - stock based compensation			(8)
Shares issued - stock based compensation				18
Net shares issued - stock based compensation	14						4
Impact from equity transactions of MPLX & ANDX	0			1			(1)
Ending balance at Jun. 30, 2018	18,818	7	(12,093)	13,688	13,589	(233)	3,860
Beginning balance at Dec. 31, 2018	44,049	10	(13,175)	33,729	14,755	(144)	8,874
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	239				(7)		246
Dividends declared on common stock	(357)				(357)
Distributions to noncontrolling interests	(305)						(305)
Contributions from noncontrolling interests	95						95
Other comprehensive loss	(7)					(7)
Shares repurchased	(885)		(885)
Shares returned - stock based compensation			(3)
Shares issued - stock based compensation				32
Net shares issued - stock based compensation	28						(1)
Impact from equity transactions of MPLX & ANDX	2			3			(1)
Other	(1)						(1)
Ending balance at Mar. 31, 2019	42,858	10	(14,063)	33,764	14,391	(151)	8,907
Beginning balance at Dec. 31, 2018	44,049	10	(13,175)	33,729	14,755	(144)	8,874
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive loss	(17)
Impact from equity transactions of MPLX & ANDX				5
Ending balance at Jun. 30, 2019	43,061	10	(14,573)	33,785	15,146	(161)	8,854
Beginning balance at Mar. 31, 2019	42,858	10	(14,063)	33,764	14,391	(151)	8,907
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	1,346				1,106		240
Dividends declared on common stock	(351)				(351)
Distributions to noncontrolling interests	(295)						(295)
Other comprehensive loss	(10)					(10)
Shares repurchased	(500)		(500)
Shares returned - stock based compensation			(10)
Shares issued - stock based compensation				19
Net shares issued - stock based compensation	11						2
Impact from equity transactions of MPLX & ANDX	1			2			(1)
Other	1						1
Ending balance at Jun. 30, 2019	$ 43,061	$ 10	$ (14,573)	$ 33,785	$ 15,146	$ (161)	$ 8,854