Stock-Based Compensation

Stock Grants

There were no stock grants granted during the three months ended March 31, 2018 and 2017. The Company recognized no stock-based compensation expense related to stock grants for the three months ended March 31, 2018 and 2017.

Restricted Stock Units

During the three months ended March 31, 2018, no restricted stock units were authorized by the Company. During the three months ended March 31, 2018, 57,708 restricted stock units vested and no restricted stock units vested during the three months ended March 31, 2017. During the three months ended March 31, 2018, 6,456 restricted stock units were forfeited under the Company's Amended and Restated Long Term Incentive Plan (the "Plan") and became available for reissuance.

The table below shows the Company's stock-based compensation expense related to the restricted stock units for the three months ended March 31, 2018 and 2017, respectively, and is included in General and administrative expenses within the Condensed Consolidated Statements of Income:



	Three Months Ended
(millions) (unaudited)	March 31, 2018		March 31, 2017
Stock-based compensation expense	$	0.1	$	0.2

As of March 31, 2018, there was $0.7 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 2.0 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 years year period.

During the three months ended March 31, 2018, the Company granted 87,750 performance share units to certain executives. During the three months ended March 31, 2018 and 2017, 11,037 and nil performance share units vested, respectively. During the three months ended March 31, 2018 and 2017, 5,719 and nil, performance share units were forfeited under the Plan and became available for reissuance. As of March 31, 2018, 14,195 shares were vested related to certain participating executives being eligible for retirement.

The table below shows the Company's stock-based compensation expense related to the Performance-Based Incentive Program for the three months ended March 31, 2018 and 2017, respectively, and is included in General and administrative expenses within the Condensed Consolidated Statements of Income:



	Three Months Ended
(millions) (unaudited)	March 31, 2018		March 31, 2017
Stock-based compensation expense	$	0.5	$	0.7

Future compensation expense for currently outstanding awards under the Performance Based Incentive Program could reach a maximum of $13.0 million. Stock-based compensation for the Performance-Based Incentive Program is expected to be recognized over a weighted average period of 2.2 years.