(10)	Stock Based Compensation

The Company recognizes compensation costs for stock options awarded to employees based on their grant-date fair value. The value of each stock option is estimated on the date of grant using the Black-Scholes option-pricing model. No stock options were granted during the three months ended March 31, 2018. The weighted-average fair value per share for the stock options granted to employees during the three months ended March 31, 2017 was $21.02.

For the three months ended March 31, 2018 and 2017, the Company recorded $1,039 and $998, respectively, in “Selling, general and administrative expenses” for stock options. As of March 31, 2018, the total compensation cost related to unvested stock options not yet recognized was $9,373. The cost will be amortized on a straight-line basis over the remaining weighted-average vesting period of 2.5 years.

The following table is a summary of the Company’s stock options:

Options	Number of Shares			Weighted Average Exercise Price
Outstanding at December 31, 2017		1,484,914		$	32.53
Exercised		(112,669	)		24.16
Forfeited or expired		(5,311	)		36.94
Outstanding at March 31, 2018		1,366,934			33.20
Exercisable at March 31, 2018		636,486		$	25.41

The aggregate intrinsic values for all stock options exercised for the three months ended March 31, 2018 and 2017 were $3,274 and $2,587, respectively. The aggregate intrinsic values for all stock options outstanding and exercisable as of March 31, 2018 were $26,314 and $17,266, respectively.

The following table is a summary of the Company’s unvested stock options, restricted stock and performance shares for which the requisite service period has not been rendered but that are expected to vest on the achievement of a performance condition:

	Unvested Stock Options					Unvested Restricted Stock				Unvested Performance Shares
	Number of Shares			Weighted- Average Grant-Date Fair Value		Number of Shares		Weighted- Average Grant-Date Fair Value		Number of Shares			Weighted- Average Grant-Date Fair Value
Unvested at December 31, 2017		757,269		$	15.20		265	$	44.23		276,250		$	42.08
Vested during period		(21,510	)		13.99		-		-		-			-
Forfeited		(5,311	)		13.90		-		-		(17,250	)		40.65
Unvested at March 31, 2018		730,448		$	15.25		265	$	44.23		259,000		$	42.17

For all periods presented, the expense recorded for restricted stock awards, and unvested restricted stock expense not yet recognized, were immaterial.

The Company granted equity-settled performance shares (“PS”) to certain executives. PS awards provide the recipient the right to receive a certain number of shares of the Company’s common stock in the future, which depends on the Company’s level of achievement of net revenue and EBITDA growth as compared to the net revenue and EBITDA growth of the members of a specified peer group of companies over a three year period. For the three months ended March 31, 2018 and 2017, the Company recorded $605 and $783, respectively, in “Selling, general and administrative expenses” related to these PS awards. As of March 31, 2018, total compensation cost related to unvested performance shares not yet recognized was $4,926. The cost will be amortized on a straight-line basis over the remaining weighted-average vesting period of 1.3 years.