MPLX LP (Tables)
 3 Months Ended
Mar. 31, 2018
Noncontrolling Interest [Abstract]  
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net
As a result of equity transactions of MPLX, we are required to adjust non-controlling interest and additional paid-in capital. Changes in MPC’s additional paid-in capital resulting from changes in its ownership interests in MPLX were as follows:
 
Three Months Ended 
 March 31,
(In millions)
2018
 
2017
Increase due to the issuance of MPLX LP common units to the public
$
4

 
$
10

Increase due to the issuance of MPLX LP common units and general partner units to MPC
1,114

 
96

Increase due to GP/IDR Exchange
1,808

 
—

Increase in MPC's additional paid-in capital
2,926

 
106

Tax impact
(546
)
 
(34
)
Increase in MPC's additional paid-in capital, net of tax
$
2,380

 
$
72