Stock-Based Compensation

9 Months Ended

Sep. 30, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-Based Compensation

Stock-Based Compensation

Stock Options

A summary of stock option activity during the nine months ended September 30, 2016 is as follows (in thousands, except for per share amounts):

	Shares		Weighted- Average Exercise Price (in dollars per share)		Weighted- Average Contractual Life (In Years)	Aggregate Intrinsic Value
Options outstanding at December 31, 2015	4,408		$	28.75
Granted	2,095		36.10
Exercised	(126	)	19.36
Cancelled	(102	)	42.12
Expired	(1	)	79.90
Options outstanding at September 30, 2016	6,274		$	31.17	8.16	$	156,384
Options exercisable at September 30, 2016	2,469		$	19.77	6.86	$	87,873
Options vested or expected to vest at September 30, 2016	6,153		$	30.98	8.14	$	154,436

The weighted-average grant-date fair value per share of options granted during the three and nine months ended September 30, 2016 was $27.19 and $19.25, respectively. As of September 30, 2016, there was approximately $70.0 million of total unrecognized compensation expense related to unvested stock options, which is expected to be recognized over a weighted-average period of approximately three years.

Restricted Stock Units

In April 2016, the Company awarded 58,500 restricted stock units ("RSUs") to employees at an average grant date fair value of $33.03 per RSU. Each RSU entitles the holder to receive one share of the Company's common stock if and when the RSU vests. The RSUs vest in four substantially equal installments on each of the first four anniversaries of the vesting commencement date, subject to the employee's continued employment on such vesting date. Compensation expense is recognized over the vesting period.

A summary of RSU activity during the nine months ended September 30, 2016 is as follows (in thousands, except for per share amounts):

	RSUs		Weighted- Average Grant Date Fair Value  (in dollars  per share)
RSUs Outstanding at December 31, 2015	—		$	—
Granted	59		33.03
Vested	—		—
Forfeited	(2	)	33.03
RSUs Outstanding at September 30, 2016	57		$	33.03

As of September 30, 2016, there was approximately $1.6 million of total unrecognized compensation expense related to unvested RSUs, which is expected to be recognized over a weighted-average period of approximately four years.

Employee Stock Purchase Plan

In September 2016, the Company initiated the first offering period for an employee stock purchase plan (“ESPP”) pursuant to which eligible employees may purchase shares of the Company’s common stock on the last day of each bi-annual offering period at 85% of the fair market value per share on the enrollment date or purchase date, whichever is lower. The offering periods run from March 1 through August 31 and from September 1 through February 28 (or 29, in a leap year) of each year.

As of September 30, 2016, the Company had recorded a liability of $0.2 million related to it's ESPP obligation.