Supplemental Cash Flow Information (Summary Of Supplemental Cash Flow Information) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Net cash provided by operating activities included:
Interest paid (net of amounts capitalized)	$ 887	$ 525		$ 478
Net income taxes paid to taxing authorities	424	904		140
Non-cash investing and financing activities:
Capital leases	172	71		0
Contribution of fixed assets to joint venture	0	337	[1]	273	[1]
Intangible asset acquired	0	45		0
Acquisition:
Fair value of MPC shares issued	19,766	0		0
Fair value of converted equity awards	$ 203	$ 0		$ 0

[1] 2017 includes MPLX’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. 2016 includes Speedway’s contribution of travel plaza locations to new joint venture with Pilot Flying J. See Note 5.