4. Stock-Based Compensation Plans

Employee Stock Purchase Plan

Under the Company’s 1999 Employee Stock Purchase Plan, as amended (the “ESPP”), a total of 4,500,000 shares of the Company’s common stock have been reserved for issuance to eligible employees. Participating employees are permitted to designate up to the lesser of $25,000 or 10% of their annual base compensation for the purchase of common stock under the ESPP. Purchases under the ESPP are made one calendar month after the end of each fiscal quarter. The price for shares of common stock purchased under the ESPP is 85% of the stock’s fair market value on the last business day of the three-month participation period. Shares issued under the ESPP during the three months ended March 31, 2017 and 2016 totaled 44,685 and 50,876, respectively.

Stock-Based Payments

A summary of stock options issued pursuant to the Company’s stock incentive plans is as follows:


	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value of In-the-Money Options
Outstanding as of December 31, 2016		6,791,375		$	15.54
Granted		864,800			20.12
Exercised		(529,697	)		13.28
Forfeited		(103,751	)		18.12
Expired		(14,783	)		20.42

Outstanding as of March 31, 2017		7,007,944		$	16.23		7.07	$	36,159,173

Exercisable as of March 31, 2017		4,167,453		$	14.45		5.78	$	28,920,839

The weighted-average grant date fair value of stock options granted during the three months ended March 31, 2017 and 2016 was $6.24 and $5.54, respectively. The Company issued treasury shares for the exercise of stock options during the three months ended March 31, 2017 and 2016. The total intrinsic value of stock options exercised during the three months ended March 31, 2017 and 2016 was $4.6 million and $0.2 million, respectively.

The fair value of options that do not vest based on the achievement of certain market conditions granted during the three months ended March 31, 2017 and 2016 were estimated on the date of grant using the Black-Scholes option-pricing model, a pricing model acceptable under U.S. GAAP, with the following weighted-average assumptions:


	Three Months Ended			Three Months Ended
	March 31, 2017			March 31, 2016
Expected life (years)		5.6			5.9
Interest rate		1.9	%		1.2	%
Volatility		29.4	%		29.7	%
Dividend yield		—			—

Expected volatilities are based on the Company’s historical common stock volatility derived from historical stock price data for historical periods commensurate with the options’ expected life. The expected life is the average number of years that the Company estimated that the options will be outstanding, based primarily on historical employee option exercise behavior. The risk-free interest rate is based on the implied yield currently available on United States Treasury zero coupon issues with a term equal to the expected term at the date of grant of the options. The expected dividend yield is zero as the Company has historically paid no dividends and does not anticipate dividends to be paid in the future.

During the three months ended March 31, 2016, the Company granted supplemental stock options with three tranches at a grant date fair value of $7.46, $7.06, and $6.50, respectively, per share. These options vest, if at all, based upon (i) tranche one - any time after the third anniversary date if the stock has traded at 133% of the exercise price for at least 20 consecutive trading days, (ii) tranche two - any time after the fourth anniversary date if the stock has traded at 167% of the exercise price for at least 20 consecutive trading days, and (iii) tranche three - any time after the fifth anniversary date if the stock has traded at 200% of the exercise price for at least 20 consecutive trading days. The employees must also remain employed with the Company as of the anniversary date in order for the options to vest. The exercise price of the supplemental stock options is the closing market price on the date the awards were granted. In order to determine the grant date fair value of the supplemental stock options, a Monte Carlo simulation model was used.

With respect to options granted that vest based on the achievement of certain market conditions, the grant date fair value of such options was estimated using the following weighted-average assumptions:


	Three Months Ended
	March 31, 2016
Expected life (years)		7.5
Interest rate		1.6	%
Volatility		41.6	%
Dividend yield		—

A summary of nonvested long-term incentive program performance share awards (“LTIP performance shares”) outstanding as of March 31, 2017 and changes during the period are as follows:


Nonvested LTIP Performance Shares	Number of Shares at Expected Attainment			Weighted- Average Grant Date Fair Value
Nonvested as of December 31, 2016		1,738,056		$	18.45
Granted		553,549			20.12
Forfeited		(51,706	)		18.24

Nonvested as of March 31, 2017		2,239,899		$	18.87

A summary of nonvested restricted share awards (“RSAs”) as of March 31, 2017 and changes during the period are as follows:


Nonvested Restricted Share Awards	Number of Restricted Share Awards			Weighted-Average Grant Date Fair Value
Nonvested as of December 31, 2016		172,108		$	20.62
Granted		446,702			20.12
Forfeited		(18,182	)		22.90

Nonvested as of March 31, 2017		600,628		$	20.18

A summary of nonvested Performance-Based Restricted Share Awards (“PBRSAs”) as of March 31, 2017 and changes during the period are as follows:


Nonvested Performance-Based Restricted Share Awards	Number of Performance-Based Restricted Share Awards			Weighted-Average Grant Date Fair Value
Nonvested as of December 31, 2016		683,667		$	23.25
Vested		(305,136	)		21.89
Forfeited		(5,536	)		23.21
Change in attainment for 2015 grants		(13,592	)		23.25

Nonvested as of March 31, 2017		359,403		$	24.41

During the three months ended March 31, 2017, a total of 305,136 shares of the PBRSAs vested. The Company withheld 109,198 of those shares to pay the employees’ portion of the minimum payroll withholding taxes.

Through December 31, 2016, the Company had accrued the compensation costs assuming an attainment level of 100% for the PBRSA grants vesting based upon forecasted 2016 earnings before income taxes, interest, depreciation and amortization (“EBITDA”). During the three months ended March 31, 2017, the Company changed the expected attainment on the PBRSAs vesting in June 2017 and June 2018 from 100% to 98% based upon actual results of the related performance target.

A summary of nonvested Retention Restricted Share Awards (“Retention RSAs”) as of March 31, 2017 and changes during the period are as follows:


Nonvested Retention Restricted Share Awards	Number of Retention Restricted Share Awards			Weighted-Average Grant Date Fair Value
Nonvested as of December 31, 2016		205,540		$	17.89
Vested		(151,871	)		17.89

Nonvested as of March 31, 2017		53,669		$	17.89

During the three months ended March 31, 2017, a total of 151,871 shares of the Retention RSAs vested. The Company withheld 52,769 of those shares to pay the employees’ portion of the minimum payroll withholding taxes.

A summary of nonvested PAY.ON RSAs as of March 31, 2017 and changes during the period are as follows:


Nonvested PAY.ON RSAs	Number of PAY.ON RSAs			Grant Date Fair Value
Nonvested at December 31, 2016		238,376		$	23.60
Forfeited		(119,188	)		23.60

Nonvested at March 31, 2017		119,188		$	23.60

During the three months ended March 31, 2017, the Company granted total shareholder return (“TSR”) awards, pursuant to the 2016 Equity and Performance Incentive Plan, to certain executive officers. TSRs are performance shares that are earned, if at all, based upon the Company’s total shareholder return as compared to a group of peer companies over a three-year performance period. The award payout can range from 0% to 200%. In order to determine the grant date fair value of the TSRs, a Monte Carlo simulation model is used. The Company recognizes compensation expense for TSRs over a three-year performance period based on the grant date fair value. The grant date fair value of the TSRs was estimated using the following weighted-average assumptions:


	Three Months Ended
	March 31, 2017
Expected life (years)		2.9
Interest rate		1.5	%
Volatility		26.5	%
Dividend Yield		—

A summary of nonvested TSRs outstanding as of March 31, 2017 and changes during the period are as follows:


Nonvested Total Shareholder Return Awards	Number of Shares at Expected Attainment		Weighted- Average Grant Date Fair Value
Nonvested as of December 31, 2016		—	$	—
Granted		233,077		24.37

Nonvested as of March 31, 2017		233,077	$	24.37

As of March 31, 2017, there were unrecognized compensation costs of $15.1 million related to nonvested stock options, $9.8 million related to the nonvested RSAs, $25.7 million related to the LTIP performance shares, $2.2 million related to nonvested PBRSAs, $0.2 million related to nonvested Retention RSAs, and $5.2 million related to the TSR shares, which the Company expects to recognize over weighted-average periods of 2.0 years, 2.7 years, 2.3 years, 1.0 years, 0.3 years, and 2.9 years, respectively.

The Company recorded stock-based compensation expenses recognized under ASC 718 for the three months ended March 31, 2017 and 2016 related to stock options, LTIP performance shares, RSAs, PBRSAs, Retention RSAs, TSR shares and the ESPP of $6.3 million and $9.7 million, respectively, with corresponding tax benefits of $2.2 million and $3.6 million, respectively. The Company recognizes compensation costs for stock option awards that vest with the passage of time with only service conditions on a straight-line basis over the requisite service period. The Company recognizes compensation costs for stock option awards that vest with service and market-based conditions on a straight-line basis over the longer of the requisite service period or the estimated period to meet the defined market-based condition.