Equity-Based Compensation Plan

3 Months Ended

Mar. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Equity-Based Compensation

Phantom Units – The following is a summary of phantom unit award activity of MPLX LP common units for the three months ended March 31, 2018:



	Number of Units		Weighted Average Fair Value
Outstanding at December 31, 2017	1,351,523		$	34.53
Granted	169,310		35.00
Settled	(217,093	)	33.83
Forfeited	(46,330	)	34.95
Outstanding at March 31, 2018	1,257,410		34.70

Performance Units – The Partnership grants performance units under the MPLX LP 2012 Incentive Compensation Plan to certain officers of the general partner and certain eligible MPC officers who make significant contributions to its business. These performance units pay out 75 percent in cash and 25 percent in MPLX LP common units and often contain both market and performance conditions based on various metrics. Market conditions are valued using a Monte Carlo valuation while performance conditions are reevaluated periodically and valued at the compensation cost associated with the performance outcome deemed most probable. During the three months ended March 31, 2018, an award was granted; however, a grant date could not be established based on the nature of the award terms. Given that a grant date cannot be established, no expense or units have been recorded. When a grant date is established, the awards fair value will be recognized over the remaining service period.

The following is a summary of the activity for performance unit awards to be settled in MPLX LP common units for the three months ended March 31, 2018:



	Number of Units
Outstanding at December 31, 2017	2,536,594
Granted	—
Settled	(538,594	)
Forfeited	(50,000	)
Outstanding at March 31, 2018	1,948,000