Consolidated Balance Sheets - USD ($) $ in Millions		Sep. 30, 2020	Dec. 31, 2019
Assets
Cash and cash equivalents		$ 28.0	$ 15.0
Receivables, net		477.0	593.0
Current Assets, Related Parties		591.0	656.0
Inventories		117.0	110.0
Other current assets		59.0	110.0
Total current assets		1,272.0	1,484.0
Equity method investments		4,081.0	5,275.0
Property, plant and equipment, net		21,615.0	22,145.0
Intangibles, net		991.0	1,270.0
Goodwill		7,657.0	9,536.0
Operating Lease, Right-of-Use Asset		323.0	365.0
Other Assets, Related Parties, Noncurrent		675.0	303.0
Other noncurrent assets		48.0	52.0
Total assets		36,662.0	40,430.0
Current liabilities:
Accounts payable		140.0	242.0
Accrued Liabilities, Current		169.0	187.0
Current Liabilities, Related Parties		364.0	1,008.0
Accrued Property Plant and Equipment Current		121.0	283.0
Accrued interest payable		207.0	210.0
Operating Lease, Liability, Current		65.0	66.0
Other current liabilities		158.0	127.0
Total current liabilities		1,531.0	2,132.0
Long-term deferred revenue		291.0	217.0
Liabilities, Related Parties, Noncurrent		281.0	290.0
Long-term debt		20,042.0	19,704.0
Deferred income taxes		12.0	12.0
Operating Lease, Liability, Noncurrent		258.0	302.0
Debt, Current		307.0	9.0
Deferred credits and other liabilities		184.0	192.0
Total liabilities		22,599.0	22,849.0
Commitments and contingencies (see Note 21)
Series A preferred units		968.0	968.0
Equity
Total MPLX LP partners’ capital		12,848.0	16,364.0
Accumulated other comprehensive loss	[1]	(16.0)	(15.0)
Noncontrolling interests		247.0	249.0
Total equity		13,095.0	16,613.0
Total liabilities, preferred units and equity		36,662.0	40,430.0
MPC
Assets
Other current assets		1.0	0.0
Operating Lease, Right-of-Use Asset		231.0	232.0
Current liabilities:
Operating Lease, Liability, Current		1.0	1.0
Operating Lease, Liability, Noncurrent		230.0	230.0
Series B Preferred Stock [Member]
Equity
Total MPLX LP partners’ capital		601.0	611.0
Limited Partners Common Units | Public
Equity
Total MPLX LP partners’ capital		9,436.0	10,800.0
Total equity		9,436.0	10,800.0
Limited Partners Common Units | MPC
Equity
Total MPLX LP partners’ capital		2,827.0	4,968.0
Total equity		2,827.0	4,968.0
LOOP and Explorer
Equity
Accumulated other comprehensive loss		(16.0)	(15.0)
Retained Earnings [Member] | MPC
Equity
Total equity		$ 0.0	$ 0.0

[1] These components of “Accumulated other comprehensive loss” are included in the computation of net periodic benefit cost by LOOP and Explorer and are therefore included on the Consolidated Statements of Income under the caption “Income/(loss) from equity method investments.”