In accordance with ASC 718, Compensation-Stock Compensation, the Company measures the cost of employee services rendered in exchange for share-based compensation based upon the grant date fair market value. The cost is recognized over the requisite service period, which is generally the vesting period unless service or performance conditions require otherwise. The Company recognizes the impact of forfeitures as they occur. The Company has granted stock options, time-vesting restricted shares and units and performance-vesting restricted shares and units.

Total equity compensation expense was $3.2 million and $7.5 million for the three months ended March 31, 2019 and 2018, respectively. Equity compensation expense for the three months ended March 31, 2018 includes approximately $4.5 million related to certain equity awards which were accelerated to vest in the first quarter of 2018 in connection with the departure of certain executives as required by their respective employment agreements. See Note 14–Restructuring and Other Separation Costs for further details. Equity compensation expense is included in selling, general and administrative expenses and in operating expenses in the accompanying unaudited condensed consolidated statements of comprehensive loss.

The activity related to the Company’s time-vesting and performance-vesting awards during the three months ended March 31, 2019 is as follows:

						Performance-Vesting Restricted shares/units
	Time-Vesting Restricted shares/units					Bonus Performance Restricted units					Long-Term Incentive Performance Restricted shares/units
	Shares/Units			Weighted Average Grant Date Fair Value per Share/Unit		Units			Weighted Average Grant Date Fair Value per Unit		Shares/Units			Weighted Average Grant Date Fair Value per Share/Unit
Outstanding at December 31, 2018		901,704		$	17.34		560,710		$	15.06		1,155,486		$	15.82
Granted		47,772		$	25.70		224,928		$	25.70		1,233,742		$	25.70
Vested		(87,079	)	$	17.12		(319,868	)	$	15.06		(27,877	)	$	15.24
Forfeited		(121,518	)	$	16.33		(246,678	)	$	15.32		(285,428	)	$	18.11
Outstanding at March 31, 2019		740,879		$	18.07		219,092		$	25.70		2,075,923		$	21.39

The activity related to the Company’s stock option awards during the three months ended March 31, 2019 is as follows:

	Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2018		764,577		$	18.05
Granted		430,390		$	25.70
Forfeited		(55,379	)	$	19.36
Expired		(8,593	)	$	18.52
Exercised		(39,928	)	$	17.90
Outstanding at March 31, 2019		1,091,067		$	21.00		7.85	$	5,188
Exercisable at March 31, 2019		556,676		$	18.28		6.47	$	4,163

The weighted average grant date fair value of stock options granted during the three months ended March 31, 2019 was $8.45. Key weighted-average assumptions utilized in the Black-Scholes Option Pricing Model for stock options granted during the three months ended March 31, 2019 were:

The Company has reserved 15,000,000 shares of common stock for issuance under its Omnibus Incentive Plan (the “Omnibus Incentive Plan”), of which approximately 8,520,000 shares are available for future issuance as of March 31, 2019.

During the three months end March 31, 2019, the Company granted performance-vesting restricted units (the “Bonus Performance Restricted Units”) in accordance with its annual bonus plan for 2019 (the “2019 Bonus Plan”). The 2019 Bonus Plan provides for bonus awards payable 50% in cash and 50% in Bonus Performance Restricted Units and is based upon the Company’s achievement of specified performance goals, as defined by the 2019 Bonus Plan, with respect to the year ended December 31, 2019 (the “Fiscal 2019”). The total number of units eligible to vest into shares of stock is based on the level of achievement of the targets for Fiscal 2019 which ranges from 0% (if below threshold performance) up to 200% (at or above maximum performance).

The Company also had an annual bonus plan for the fiscal year ended December 31, 2018 (“Fiscal 2018”), under which certain employees were eligible to vest in Bonus Performance Restricted Units based upon the Company’s achievement of certain performance goals with respect to Fiscal 2018. Based on the Company’s actual Fiscal 2018 results, a portion of these Bonus Performance Restricted Units vested in the three months ended March 31, 2019 and the remaining forfeited in accordance with their terms.

During the three months ended March 31, 2019, the Company granted long-term incentive plan awards for 2019 (the “2019 Long-Term Incentive Grant”) which were comprised of nonqualified stock options (the “Long-Term Incentive Options”) and performance-vesting restricted units (the “Long-Term Incentive Performance Restricted Units”) (collectively, the “Long-Term Incentive Awards”). Long-Term Incentive Awards for 2019, 2020 and 2021 combined were granted to certain employees during the three months ended March 31, 2019. The Company does not expect additional Long-Term Incentive Awards to be granted to these employees until the earlier of 2022 or in the year when the Company’s three-year performance goal is achieved, if sooner than fiscal year 2021.

Long-Term Incentive Options vest over three years, with one-third vesting on each anniversary of the date of grant, subject to continued employment through the applicable vesting date. Equity compensation expense for these options is recognized using the straight line method.

The Long-Term Incentive Performance Restricted Units are expected to vest following the end of the three-year performance period beginning on January 1, 2019 and ending on December 31, 2021 based upon the Company’s achievement of specified performance goals for Fiscal 2021, as defined by the 2019 Long-Term Incentive Grant. The total number of Long-Term Incentive Performance Restricted Units eligible to vest will be based on the level of achievement of the performance goals and ranges from 0% (if below threshold performance) up to 100% (for target or above performance). Upon achievement of the performance goals, only 50% of the award for a given level of performance will vest, with the remaining 50% subject to a one-year performance test period. The goal achieved must be met again or exceeded the next fiscal year before the remaining units are earned.

During the three months ended March 31, 2019, the Company also granted time-restricted units which vest over three years to certain employees, with one-third vesting on each anniversary of the date of grant, subject to continued employment through the applicable vesting date. Equity compensation expense is recognized using the straight line method.

The Company also has outstanding long-term incentive time restricted shares, long-term incentive performance restricted shares and long-term incentive options granted under previous long-term incentive plan grants. During the three months ended March 31, 2019, a portion of the previously granted long-term incentive performance restricted shares related to completed performance periods vested, with the remainder forfeiting in accordance with their terms. The remaining outstanding long-term incentive performance restricted shares are eligible to vest based upon the Company’s achievement of pre-established performance goals for the respective performance period, as defined.

The Company recognizes equity compensation expense for its performance-vesting restricted awards ratably over the related performance period, if the performance condition is probable of being achieved. Based on the Company’s progress towards its respective performance goals, a portion of its performance-vesting restricted awards are considered probable of vesting as of March 31, 2019; therefore, equity compensation expense has been recorded accordingly. If the probability of vesting related to these awards changes in a subsequent period, all equity compensation expense related to those awards that would have been recorded over the requisite service period had the awards been considered probable at the new percentage from inception, will be recorded as a cumulative catch-up at such subsequent date.