(8) Share-based Compensation

The Company’s 2013 Stock Incentive Plan (as amended, the “2013 Equity Plan”) authorizes the issuance of various types of share-based awards to the Company’s employees, officers, directors, and other eligible participants. In March 2018, the Board of Directors authorized, and in May 2018 the Company’s stockholders approved, a further amendment to the 2013 Equity Plan to, among other things, increase the total number of shares of the Company’s class A common stock authorized for issuance under the 2013 Equity Plan from 1,700,000 shares to 2,300,000 shares. As of June 30, 2018, there were 565,000 shares of class A common stock reserved and available for future issuance under the 2013 Equity Plan.

Stock option awards

During the second quarter of 2018, stock options to purchase an aggregate of 102,500 shares of class A common stock were granted pursuant to the 2013 Equity Plan. As of June 30, 2018, there were options to purchase 1,481,233 shares of class A common stock outstanding under the 2013 Equity Plan.

The following table summarizes the Company’s stock option activity (in thousands, except per share data and years) for the three months ended June 30, 2018:

	Stock Options Outstanding
				Weighted Average		Aggregate		Weighted Average
				Exercise Price		Intrinsic		Remaining Contractual
	Shares			Per Share		Value		Term (Years)
Balance as of April 1, 2018		1,463		$	140.83
Granted		103			128.27
Exercised		(21	)		121.13	$	196
Forfeited/Expired		(64	)		163.25
Balance as of June 30, 2018		1,481		$	139.26
Exercisable as of June 30, 2018		724			137.07		3,316		5.7
Expected to vest as of June 30, 2018		757			141.36		19		9.3
Total		1,481		$	139.26		3,335		7.5

Stock options outstanding as of June 30, 2018 are comprised of the following range of exercise prices per share (in thousands, except per share data and years):

	Stock Options Outstanding at June 30, 2018
			Weighted Average		Weighted Average
			Exercise Price		Remaining Contractual
Range of Exercise Prices per Share	Shares		Per Share		Term (Years)
$117.85 - $120.00		23	$	118.50		5.8
$120.01 - $150.00		1,109	$	126.92		7.9
$150.01 - $180.00		178	$	167.68		4.9
$180.01 - $201.25		171	$	192.39		7.9
Total		1,481	$	139.26		7.5

An aggregate of 157,500 stock options with an aggregate fair value of $8.9 million vested during the three months ended June 30, 2018. The weighted average grant date fair value of stock option awards using the Black-Scholes pricing model was $50.76 and $72.78 for each share subject to a stock option granted during the three months ended June 30, 2018 and 2017, respectively, based on the following assumptions:

	Three months ended
	June 30,
	2018		2017
Expected term of options in years	6.3		6.3
Expected volatility	34.6% - 34.9	%		37.4	%
Risk-free interest rate	2.7% - 2.8	%		1.9	%
Expected dividend yield	0.0	%		0.0	%

For the three and six months ended June 30, 2018, the Company recognized approximately $3.4 million and $8.1 million, respectively, in share-based compensation expense from stock options granted under the 2013 Equity Plan. For the three and six months ended June 30, 2017, the Company recognized approximately $3.8 million and $6.9 million, respectively, in share-based compensation expense from stock options granted under the 2013 Equity Plan. As of June 30, 2018, there was approximately $37.6 million of total unrecognized share-based compensation expense related to unvested stock options. The Company expects to recognize this remaining share-based compensation expense over a weighted average vesting period of approximately 3.3 years.

Other stock-based awards

During the second quarter of 2018, the Company granted certain awards characterized as “other stock-based awards” under the 2013 Equity Plan. These other stock-based awards are similar to stock options, but these awards are settled in cash only and not in shares of the Company’s class A common stock. Upon exercise of this award, the participant would be entitled to receive an amount in cash equal to the fair market value of the Company’s class A common stock in excess of a stated exercise price. These awards vest in equal annual installments over a four-year period (unless accelerated upon a change in control event (as defined in the applicable award agreement) or otherwise in accordance with the provisions of the 2013 Equity Plan or applicable award agreement). During the second quarter of 2018, the Company granted such other stock-based awards with respect to an aggregate of 10,000 underlying shares of class A common stock with a weighted average exercise price per share of $129.90 pursuant to the 2013 Equity Plan. Similar to stock option awards, the Company recognizes share-based compensation expense associated with these awards on a straight-line basis over the award’s requisite service period (generally, the vesting period), with share-based compensation expense based on the fair value of the award estimated using the Black-Scholes option pricing model. However, due to the required cash settlement feature, these awards are classified as liabilities in the Company’s Consolidated Balance Sheets and the fair value of the awards is remeasured each quarterly reporting period with resulting adjustments to share-based compensation expense recorded until the earlier of settlement or expiration. For each of the three and six months ended June 30, 2018, the Company did not recognize a material amount in share-based compensation expense from these awards. As of June 30, 2018, there was approximately $0.5 million of total unrecognized share-based compensation expense related to these awards. The Company expects to recognize this remaining share-based compensation expense over a weighted average vesting period of approximately 3.9 years, subject to additional fair value adjustments through the earlier of settlement or expiration.