Stock-Based Compensation

The Company measures stock-based compensation expense at the grant date, based on the estimated fair value of the award, and the expense is recognized over the requisite employee service period or performance period (generally the vesting period) for awards expected to vest. The Company accounts for forfeitures of stock-based awards as they occur.

The Company has an amended and restated long-term incentive plan (the "Plan") that was adopted in conjunction with its initial public offering in 2004. In February 2008, the Board of Directors approved an amendment to the Plan, subject to stockholder approval, that increased the maximum number of shares of common stock available for awards under the Plan from 2,000,000 to 2,175,000 and extended the Plan's termination date. Company stockholders approved this Plan amendment on April 22, 2008, and the Plan now terminates twenty years from the date of such approval, or April 22, 2028. On March 13, 2013, the Board approved an amendment to the Plan, subject to stockholder approval, that increased the number of shares of common stock available for awards under the Plan from 2,175,000 to 2,975,000. Company stockholders approved this Plan amendment on April 24, 2013. Forfeited and expired options under the Plan become generally available for reissuance. At December 31, 2017, 248,534 shares remained available for award under the Plan.

Stock Options and Grants

There were no options granted during the years ended December 31, 2017, 2016 and 2015. The Company recognized no stock-based compensation expense related to stock options for the years ended December 31, 2017, 2016 and 2015 as all options previously granted are fully vested.

The following is a summary of Company authorized vested stock grants to certain directors for the year ended December 31, 2017, 2016 and 2015. Stock-based compensation expense related to vested stock grants are included in General and administrative expenses within the Consolidated Statements of Income.



	Year Ended December 31,
(millions, except stock grants)	2017		2016		2015
Vested stock grants	16,428		32,180		32,357
Stock-based compensation expense	$	0.5	$	0.7	$	0.7

Restricted Stock Units

No grants of restricted stock units were authorized during the year ended December 31, 2017.

During the year ended December 31, 2016, the Company authorized certain one-time grants of 4,020 restricted stock units to certain executives that vest five years from date of issuance. The restricted stock unit agreements are designed to reward performance over a five-year period.

During the year ended December 31, 2015, the Company authorized one-time grants of 3,963 restricted stock units to certain executives that vest three years from date of issuance. The restricted stock unit agreements are designed to reward performance over a three-year period.

The fair value of restricted stock units is determined using the market value of the Company's common stock on the date of the grant, and compensation expense is recognized over the vesting period.

A summary of the status of the restricted stock units as of December 31, 2017, and changes during the year ended December 31, 2017, 2016 and 2015, are presented below:



	Shares		Weighted Average Grant-Date Fair Value
Nonvested as of December 31, 2014	555,700		$	19.57
Issued	12,589		23.65
Vested	(150,073	)	20.77
Forfeited	(16,500	)	19.45
Nonvested as of December 31, 2015	401,716		$	19.25
Issued	4,020		24.87
Vested	(54,215	)	18.33
Forfeited	(17,324	)	19.68
Nonvested as of December 31, 2016	334,197		$	19.45
Issued	22,000		18.25
Vested	(26,399	)	18.98
Forfeited	(4,537	)	21.92
Nonvested as of December 31, 2017	325,261		$	19.37

The table below shows the Company's stock-based compensation expense related to the restricted stock units for the years ended December 31, 2017, 2016 and 2015, and is included in General and administrative expenses within the Consolidated Statements of Income.



	Year Ended December 31,
(millions)	2017		2016		2015
Stock-based compensation expense	$	0.9	$	0.9	$	1.6

Unrecognized stock-based compensation expense related to the restricted stock units for the years ended December 31, 2017, 2016 and 2015, is shown in the table below, along with the weighted average periods in which the expense will be recognized.



	Year Ended December 31,
(millions)	2017		2016		2015
Unrecognized stock-based compensation	$	0.9	$	1.7	$	2.7
Weighted average (years)	2.1 years		2.8 years		3.8 years

Performance Share Units

In September 2014, the Board of Directors authorized a performance-based incentive program under the Plan ("Performance-Based Incentive Program"), whereby the Company will issue performance share units to certain executive management individuals 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 the cumulative three-year period and recipients satisfy service-based vesting requirements. The stock-based compensation expense associated with unvested performance-based incentives 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.

In March 2017, the Board of Directors authorized a performance-based incentive program under the Company's Long-Term Incentive Plan ("2017 Performance-Based Incentive Program"). The 2017 Performance-Based Incentive Program is similar to the 2015 and 2016 Performance-Based Incentive Program, with the exception of the number of shares ultimately to be issued is based on the achievement of pre-tax free cash flow over the cumulative three-year period of 2017 through 2019.

During 2017, certain participating executives became vested in Performance-Based Incentive Program shares based on retirement eligibility and as a result $0.2 million of stock-based compensation related to 7,529 shares were recognized in General and administrative expenses, and which continue to be subject to achieving cumulative pre-tax free cash flow over the respective three-year periods. Additionally, participating executives became vested in the Performance-Based Incentive Program shares based on meeting eligibility for vesting at the end of the three-year performance period of 2015 through 2017. As a result, 54,390 shares were vested to these participating executives as of December 31, 2017.

In April 2016, the Board of Directors authorized another performance-based incentive program under the Company's Long-Term Incentive Plan ("2016 Performance-Based Incentive Program"). The 2016 Performance-Based Incentive Program is similar to the 2015 Performance-Based Incentive Program, with the exception of the number of shares ultimately to be issued is based on the achievement of pre-tax free cash flow over the cumulative three-year period of 2016 through 2018.

During 2016, certain participating executives became vested in Performance-Based Incentive Program shares based on retirement eligibility and as a result $0.1 million of stock-based compensation related to 2,083 shares were recognized in General and administrative expenses, and which continue to be subject to achieving cumulative pre-tax free cash flow over the respective three-year periods. Additionally, participating executives became vested in the Performance-Based Incentive Program shares based on meeting eligibility for vesting at the end of the three-year performance period of 2014 through 2016. As a result, 82,334 shares were vested to these participating executives as of December 31, 2016.

During 2015, certain participating executives became vested in the Performance-Based Incentive Program shares based on retirement eligibility and as a result $0.1 million of stock-based compensation related to 6,915 shares were recognized in General and administrative expenses within the Consolidated Statements of Income, and which continue to be subject to achieving cumulative pre-tax free cash flow over the three-year period of 2015 through 2017.

A summary of the status of the performance share units as of December 31, 2017, and changes during the year ended December 31, 2017, 2016 and 2015 are presented below:



	Shares		Weighted Average Grant-Date Fair Value
Nonvested as of December 31, 2014	79,430		$	18.96
Issued (1)	125,392		21.64
Vested	(6,915	)	19.91
Forfeited	(24,056	)	20.30
Nonvested as of December 31, 2015	173,851		20.63
Issued	99,466		23.72
Vested	(84,417	)	19.15
Forfeited	(29,423	)	22.52
Nonvested as of December 31, 2016	159,477		22.99
Issued (2)	29,494		29.51
Vested	(61,919	)	22.63
Forfeited	(11,770	)	25.86
Nonvested as of December 31, 2017	115,282		$	28.01

(1) Includes an additional 19,855 shares of performance adjustments made at a weighted average grant-date fair value of $19.02.

(2) Includes a reduction of 59,091 shares of performance adjustments made at a weighted average grant-date fair value of $26.07.

The table below shows the Company's stock-based compensation expense related to the Performance-Based Incentive Program for the years ended December 31, 2017, 2016 and 2015, and is included in General and administrative expenses within the Consolidated Statements of Income.



	Year Ended December 31,
(millions)	2017		2016		2015
Stock-based compensation	$	1.3	$	1.8	$	1.3

During the years ended December 31, 2017, 2016 and 2015, respectively, 11,770, 29,423 and 24,056 performance-based shares were forfeited under the Long-Term Incentive Program and became available for reissuance.

Future compensation expense for currently outstanding awards under the Performance-Based Incentive Program could reach a maximum of $7.3 million. Stock-based compensation for the Performance-Based Incentive Program is expected to be recognized over a weighted average period of 1.7 years.