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Equity-Based Compensation Plan
9 Months Ended
Sep. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]  
Equity-Based Compensation Plan
Equity-Based Compensation

Phantom Units—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 Units—We grant performance units under the MPLX LP 2012 Incentive Compensation Plan to certain officers of our general partner and certain eligible MPC officers who make significant contributions to our business. These performance units pay out 75 percent in cash and 25 percent in MPLX LP common units. The performance units paying out in units are accounted for as equity awards and had a weighted-average grant date fair value per unit of $1.03 for 2015, as calculated using a Monte Carlo valuation model.

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