Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Debt - MPC 364-Day Bank Revolving Credit Facility (Details) - USD ($) $ in Millions	Jul. 26, 2019	Jun. 30, 2019
Debt Instrument [Line Items]
Current borrowing capacity		$ 11,100
MPC 364-day revolver due September 2019
Debt Instrument [Line Items]
Current borrowing capacity		$ 1,000
Subsequent Event \| MPC 364-day revolver due September 2020
Debt Instrument [Line Items]
Current borrowing capacity	$ 1,000