Debt (MPLX Senior Notes) (Details) - MPLX - Senior Notes - USD ($) $ in Millions			3 Months Ended
	Sep. 03, 2021	Jan. 15, 2021	Sep. 30, 2022	Dec. 31, 2022	Aug. 11, 2022	Mar. 14, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Long-term debt outstanding				$ 20,100			$ 18,600
Senior notes, 3.500% due December 2022
Debt Instrument [Line Items]
Long-term debt outstanding				0			486
Repayments of debt			$ 500
Senior notes, 3.500% due December 2022 | ANDX
Debt Instrument [Line Items]
Repayments of debt			14
Senior notes, 3.375% due March 2023
Debt Instrument [Line Items]
Long-term debt outstanding				0			500
Repayments of debt			$ 500
Senior notes, 4.500% due July 2023
Debt Instrument [Line Items]
Long-term debt outstanding				989			989
Senior notes, 4.875% due December 2024
Debt Instrument [Line Items]
Long-term debt outstanding				1,149			1,149
Senior notes, 4.000% due February 2025
Debt Instrument [Line Items]
Long-term debt outstanding				500			500
Senior notes, 4.875% due June 2025
Debt Instrument [Line Items]
Long-term debt outstanding				1,189			1,189
Senior notes, 1.750% due March 2026
Debt Instrument [Line Items]
Long-term debt outstanding				1,500			1,500
Senior notes, 4.125% due March 2027
Debt Instrument [Line Items]
Long-term debt outstanding				1,250			1,250
Senior notes, 4.250% due December 2027
Debt Instrument [Line Items]
Long-term debt outstanding				732			732
Senior notes, 4.000% due March 2028
Debt Instrument [Line Items]
Long-term debt outstanding				1,250			1,250
Senior notes, 4.800% due February 2029
Debt Instrument [Line Items]
Long-term debt outstanding				750			750
Senior notes, 2.650% due August 2030
Debt Instrument [Line Items]
Long-term debt outstanding				1,500			1,500
Senior notes, 4.950% due September 2032
Debt Instrument [Line Items]
Long-term debt outstanding				1,000			0
Debt instrument, face amount					$ 1,000
Senior notes, 4.500% due April 2038
Debt Instrument [Line Items]
Long-term debt outstanding				1,750			1,750
Senior notes, 5.200% due March 2047
Debt Instrument [Line Items]
Long-term debt outstanding				1,000			1,000
Senior notes, 5.200% due December 2047
Debt Instrument [Line Items]
Long-term debt outstanding				487			487
Senior notes, 4.700% due April 2048
Debt Instrument [Line Items]
Long-term debt outstanding				1,500			1,500
Senior notes, 5.500% due February 2049
Debt Instrument [Line Items]
Long-term debt outstanding				1,500			1,500
Senior notes, 4.950% due March 2052
Debt Instrument [Line Items]
Long-term debt outstanding				1,500			0
Debt instrument, face amount						$ 1,500
Senior notes, 4.900% due April 2058
Debt Instrument [Line Items]
Long-term debt outstanding				500			500
Senior notes, 5.250% due January 2025
Debt Instrument [Line Items]
Repayments of debt		$ 750
Floating rate senior notes due September 2022
Debt Instrument [Line Items]
Repayments of debt	$ 1,000
MarkWest | MarkWest senior notes, 4.500% - 5.500% due 2023 - 2025
Debt Instrument [Line Items]
Long-term debt outstanding				23			23
ANDX | ANDX senior notes, 3.500% - 6.375% due 2019 - 2047
Debt Instrument [Line Items]
Long-term debt outstanding				$ 31			$ 45