v3.3.0.814
Equity-Based Compensation Plan (Tables)
9 Months Ended
Sep. 30, 2015
Phantom Units [Member]  
Equity Transactions And Share Based Compensation [Line Items]  
Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]
The following is a summary of phantom unit award activity of MPLX LP common limited partner units for the nine months ended September 30, 2015:
 
Number
of Units
 
Weighted
Average
Fair Value
Outstanding at December 31, 2014
100,769

 
$
41.66

Granted
35,630

 
80.16

Settled
(32,313
)
 
40.18

Outstanding at September 30, 2015
104,086

 
55.30

Performance Shares [Member]  
Equity Transactions And Share Based Compensation [Line Items]  
Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]
The following is a summary of the equity-classified performance unit award activity for the nine months ended September 30, 2015:
 
Number of
Units
Outstanding at December 31, 2014
924,143

Granted
597,249

Outstanding at September 30, 2015
1,521,392