Stock-Based Compensation

3 Months Ended

Mar. 31, 2017

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 three months ended March 31, 2017 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, 2016	6,374		$	31.60
Granted	1,365		45.36
Exercised	(76	)	23.59
Cancelled	(45	)	35.94
Expired	—		—
Options outstanding at March 31, 2017	7,618		$	34.12	8.11	$	77,755
Options exercisable at March 31, 2017	3,414		$	24.33	7.02	$	60,263
Options vested or expected to vest at March 31, 2017	7,618		$	34.12	8.11	$	77,755

The weighted-average grant-date fair value per share of options granted during the three months ended March 31, 2017 was $24.82. As of March 31, 2017, there was approximately $89.0 million of total unrecognized compensation expense related to unvested stock options, which is expected to be recognized over a weighted-average period of approximately 2.9 years.

Restricted Stock Units

The Company awards restricted stock units ("RSUs") to employees under its 2011 Equity Incentive Plan. 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 with, or service to, the Company on such vesting date. Compensation expense is recognized on a straight line basis. In February 2017, the Company awarded 84,950 restricted stock units ("RSUs") to employees at an average grant date fair value of $45.65 per RSU.

A summary of RSU activity during the three months ended March 31, 2017 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, 2016	57		$	33.03
Granted	85		45.65
Vested	—		—
Forfeited	(1	)	45.65
RSUs Outstanding at March 31, 2017	141		$	41.95

As of March 31, 2017, there was approximately $5.4 million of total unrecognized compensation expense related to unvested RSUs, which is expected to be recognized over a weighted-average period of approximately 3.5 years.

Employee Stock Purchase Plan

In September 2016, the Company initiated the first offering period under the Company's 2016 Employee Stock Purchase Plan (the “ESPP”), pursuant to which eligible employees may purchase shares of the Company’s common stock on the last day of each predetermined six-month offering period at 85% of the lower of the fair market value per share at the beginning or end of the applicable offering period. The offering periods run from March 1 through August 31 and from September 1 through February 28 (or February 29, in a leap year) of each year.

As of March 31, 2017, the Company had recorded a liability of $0.3 million related to its ESPP obligations.