Debt - Outstanding Borrowings (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014		Dec. 31, 2013
Debt Instrument [Line Items]
Total	$ 3,639		$ 3,395
Unamortized discount	(10)		(10)
Fair value adjustments	9	[1]	11	[1]
Amounts due within one year	(26)		(23)
Total long-term debt due after one year	3,612		3,373
Interest Rate Swap
Debt Instrument [Line Items]
Deferred gain on discontinuation of interest rate fair value hedge	20
Consolidated subsidiaries: | Capital Lease Obligations
Debt Instrument [Line Items]
Capital lease obligations	384		395
Debt instrument maturity year, start	Jan. 01, 2014
Debt instrument maturity year, end	Dec. 31, 2028
MPC Revolver
Debt Instrument [Line Items]
Borrowings outstanding	0		0
Line of credit facility, expiration date	Sep. 14, 2017
3.500% senior notes due March 1, 2016
Debt Instrument [Line Items]
Senior notes	750		750
Debt instrument, maturity date	Mar. 01, 2016
Debt instrument, interest rate	3.50%
5.125% senior notes due March 1, 2021
Debt Instrument [Line Items]
Senior notes	1,000		1,000
Debt instrument, maturity date	Mar. 01, 2021
Debt instrument, interest rate	5.125%
6.500% senior notes due March 1, 2041
Debt Instrument [Line Items]
Senior notes	1,250		1,250
Debt instrument, maturity date	Mar. 01, 2041
Debt instrument, interest rate	6.50%
MPLX Revolver | MPLX Operations LLC
Debt Instrument [Line Items]
Borrowings outstanding	255		0
Line of credit facility, expiration date	Oct. 31, 2017
Trade Receivables Securitization | Consolidated subsidiaries:
Debt Instrument [Line Items]
Trade receivables securitization facility	$ 0		$ 0
Line of credit facility, expiration date	Dec. 31, 2016

[1] The $20 million gain on the termination of our interest rate swap agreements in 2012 is being amortized over the remaining life of the 3.50 percent senior notes.