Stock-Based Compensation

Stock Grants

There were 12,736 and 16,428 stock grants granted during the three and six months ended June 30, 2018 and 2017, respectively. The Company recognized $0.5 million and $0.5 million of stock-based compensation expense related to stock grants for the three and six months ended June 30, 2018 and 2017, respectively.

Restricted Stock Units

During the six months ended June 30, 2018, 52,306 restricted stock units were authorized by the Company. No restricted stock units were issued during the six months ended June 30, 2017. During the six months ended June 30, 2018 and 2017, 57,708 and 4,399 restricted stock units vested, respectively. During the six months ended June 30, 2018 and 2017, 6,456 and 4,537 restricted stock units were forfeited under the Company's Long-Term Incentive Plan, as Amended and Restated (the "Plan") and became available for reissuance, respectively.

The table below shows the Company's stock-based compensation expense related to the restricted stock units for the three and six months ended June 30, 2018 and 2017, respectively, and is included in General and administrative expenses within the Condensed Consolidated Statements of Income:



	Three Months Ended				Six Months Ended
(millions) (unaudited)	June 30, 2018		June 30, 2017		June 30, 2018		June 30, 2017
Stock-based compensation expense	$	0.3	$	0.2	$	0.4	$	0.4

As of June 30, 2018, there was $2.2 million of unrecognized stock-based compensation costs related to the restricted stock units that are expected to be recognized over a weighted average remaining period of approximately 2.6 years.

Performance Share Units

In September 2014, the Board of Directors authorized a performance-based incentive program under the Company’s Plan (“Performance-Based Incentive Program”), whereby the Company will issue performance share units to certain executives that represent shares potentially issuable in the future. The objective of the Performance-Based Incentive Program is to link compensation to business performance, encourage ownership of Company stock, retain executive talent, and reward executive performance. The Performance-Based Incentive Program provides participating executives with the opportunity to earn vested common stock if certain performance targets for pre-tax free cash flow are achieved over a three year performance period and recipients satisfy service-based vesting requirements. The stock-based compensation expense associated with unvested performance share units are recognized on a straight-line basis over the shorter of the vesting period or minimum service period and dependent upon the probable outcome of the number of shares that will ultimately be issued based on the achievement of pre-tax free cash flow over the cumulative three-year period.

During the six months ended June 30, 2018 and 2017, the Company granted 99,718 and 76,120 performance share units to certain executives, respectively. During the six months ended June 30, 2018 and 2017, 11,037 and 14,195 performance share units vested, respectively, related to certain participating executives being eligible for retirement. During the six months ended June 30, 2018 and 2017, 5,719 and 11,770 performance share units were forfeited under the Plan and became available for reissuance, respectively.

The table below shows the Company's stock-based compensation expense related to the Performance-Based Incentive Program for the three and six months ended June 30, 2018 and 2017, respectively, and is included in General and administrative expenses within the Condensed Consolidated Statements of Income:



	Three Months Ended				Six Months Ended
(millions) (unaudited)	June 30, 2018		June 30, 2017		June 30, 2018		June 30, 2017
Stock-based compensation expense	$	0.6	$	0.5	$	1.1	$	1.2

Future compensation expense for currently outstanding awards under the Performance-Based Incentive Program could reach a maximum of $12.9 million. Stock-based compensation for the Performance-Based Incentive Program is expected to be recognized over a weighted average period of 2.1 years.