Incentive Plans

Stock-based compensation

For the three months ended March 31, 2013, the Company recorded $27.6 million of stock-based compensation expense for all plans, as compared to $21.3 million for the same period of 2012. As of March 31, 2013, there was $198.5 million of unrecognized compensation expense related to unvested share- and unit-based compensation plan awards, including $47.5 million attributable to stock-based awards that are expected to be settled in cash on their vesting date, rather than in equity shares ("Liability Awards"). This compensation will be recognized over the remaining vesting periods of the awards, which is a period of less than three years on a weighted average basis. As of March 31, 2013 and December 31, 2012, accounts payable – due to affiliates includes $5.8 million and $18.8 million, respectively, of liabilities attributable to Liability Awards.

The following table summarizes the activity that occurred during the three months ended March 31, 2013, for each type of share-based incentive award issued by Pioneer:



	Restricted Stock Equity Awards		Restricted Stock Liability Awards		Performance Units	Stock Options		Pioneer Southwest LTIP Restricted Units	Pioneer Southwest LTIP Phantom Units
Outstanding at December 31, 2012	1,512,762		405,916		91,370	467,486		7,496	102,644
Awards granted	397,439		238,269		94,917	—		—	32,242
Awards vested	(476,717	)	(178,143	)	—	—		—	(35,118	)
Options exercised	—		—		—	(12,818	)	—	—
Awards forfeited	(3,834	)	(5,015	)	—	—		—	—
Outstanding as of March 31, 2013	1,429,650		461,027		186,287	454,668		7,496	99,768

Postretirement Benefit Obligations

As of March 31, 2013 and December 31, 2012, the Company had $9.1 million and $9.7 million, respectively, of unfunded accumulated postretirement benefit obligations, the current and noncurrent portions of which are included in other current liabilities and other liabilities, respectively, in the accompanying consolidated balance sheets. These obligations are comprised of five unfunded plans, of which four relate to predecessor entities that the Company acquired in prior years, and one funded plan that the Company assumed sponsorship for in conjunction with the acquisition of Premier Silica.

The unfunded plans had no assets as of March 31, 2013 or December 31, 2012. The Company's funding policy for the Premier Silica plan is to contribute amounts sufficient to meet legal funding requirements, plus any additional amounts that the Company may determine to be appropriate considering the funded status of the plan, tax deductibility, the cash flow generated by the Company, and other factors. The Company continually reassesses the amount and timing of any discretionary contributions and may elect to make such contributions in future periods.