Equity and Stock-based Compensation (Tables)
|
12 Months Ended |
Dec. 31, 2019 |
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] |
|
Summary of Common Stock Reserved for Future Issuance |
Shares of Common Stock outstanding, shares of stock plans outstanding and shares reserved for future issuance related to stock options and RSU grants and the Company’s Employee Stock Purchase Plan (“ESPP”) purchases are as follows (in thousands):
|
|
December 31, |
|
|
|
2019 |
|
|
2018 |
|
Common stock outstanding |
|
|
87,657 |
|
|
|
85,432 |
|
Stock options outstanding |
|
|
10,018 |
|
|
|
10,430 |
|
RSUs outstanding |
|
|
1,483 |
|
|
|
1,428 |
|
Common stock warrants outstanding |
|
|
— |
|
|
|
4 |
|
Shares reserved for future stock options and RSUs grant |
|
|
7,725 |
|
|
|
6,041 |
|
Shares reserved for future ESPP offering |
|
|
3,337 |
|
|
|
2,618 |
|
Total shares of common stock reserved |
|
|
110,220 |
|
|
|
105,953 |
|
|
Summary of Stock Option Transactions |
Stock option transactions, including forfeited options granted under the 2014 Plan as well as prior plans, are summarized below:
|
|
Shares
(In thousands) |
|
|
Weighted
Average
Exercise per
Share |
|
|
Weighted
Average
Remaining Contractual
Life
(In Years) |
|
|
Aggregate
Intrinsic Value
(In thousands) |
|
Outstanding at December 31, 2018 |
|
|
10,430 |
|
|
$ |
20.25 |
|
|
|
|
|
|
|
|
|
Granted |
|
|
1,909 |
|
|
|
53.75 |
|
|
|
|
|
|
|
|
|
Exercised |
|
|
(1,642 |
) |
|
|
10.15 |
|
|
|
|
|
|
|
|
|
Expired |
|
|
(21 |
) |
|
|
50.40 |
|
|
|
|
|
|
|
|
|
Forfeited |
|
|
(658 |
) |
|
|
44.65 |
|
|
|
|
|
|
|
|
|
Outstanding at December 31, 2019 |
|
|
10,018 |
|
|
|
26.63 |
|
|
|
5.17 |
|
|
$ |
193,226 |
|
Vested and expected to vest, December 31, 2019 |
|
|
10,018 |
|
|
|
26.63 |
|
|
|
5.17 |
|
|
|
193,226 |
|
Exercisable at December 31, 2019 |
|
|
7,318 |
|
|
$ |
18.63 |
|
|
|
3.89 |
|
|
$ |
183,707 |
|
|
Summary of RSU Activity |
The following table summarizes RSU activity:
|
|
Shares
(In thousands) |
|
|
Fair Value at Grant |
|
Unvested at December 31, 2018 |
|
|
1,428 |
|
|
$ |
38.26 |
|
Granted |
|
|
1,110 |
|
|
|
54.74 |
|
Vested |
|
|
(715 |
) |
|
|
37.71 |
|
Forfeited |
|
|
(340 |
) |
|
|
46.15 |
|
Unvested at December 31, 2019 |
|
|
1,483 |
|
|
$ |
49.05 |
|
|
Schedule of Allocated Stock-Based Compensation Expense |
Stock-based compensation expense allocated to research and development and selling, general and administrative expense for the years ended December 31, 2019, 2018 and 2017 was as follows (in thousands):
|
|
Years Ended December 31, |
|
|
|
2019 |
|
|
2018 |
|
|
2017 |
|
Research and development |
|
$ |
41,015 |
|
|
$ |
30,491 |
|
|
$ |
21,807 |
|
Selling, general and administrative |
|
|
25,252 |
|
|
|
21,651 |
|
|
|
15,732 |
|
Total stock-based compensation expense |
|
$ |
66,267 |
|
|
$ |
52,142 |
|
|
$ |
37,539 |
|
|
Schedule of Assumptions used to Estimate Fair Value of Stock Options Granted and Employee Stock Purchase Plans |
The assumptions used to estimate the fair value of stock options granted and ESPPs using the Black-Scholes option valuation model were as follows:
|
|
Years Ended December 31, |
|
|
2019 |
|
|
|
2018 |
|
|
|
2017 |
|
|
Stock Options |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Expected term (in years) |
|
|
5.3 |
|
|
|
|
5.4 |
|
|
|
|
5.7 |
|
|
Expected volatility |
|
|
68.0 |
|
% |
|
|
67.9 |
|
% |
|
|
71.5 |
|
% |
Risk-free interest rate |
|
|
2.4 |
|
% |
|
|
2.7 |
|
% |
|
|
2.2 |
|
% |
Expected dividend yield |
|
|
— |
|
|
|
|
— |
|
|
|
|
— |
|
|
Weighted average estimated fair value |
|
$ |
31.98 |
|
|
|
$ |
32.12 |
|
|
|
$ |
16.96 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
ESPPs |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Expected term (in years) |
|
0.5 - 2.0 |
|
|
|
0.5 - 2.0 |
|
|
|
0.5 - 2.0 |
|
|
Expected volatility |
|
48.1 - 62.1 |
|
% |
|
47.3 - 75.3 |
|
% |
|
52.8 - 77.2 |
|
% |
Risk-free interest rate |
|
1.3 - 2.9 |
|
% |
|
0.8 - 2.9 |
|
% |
|
0.5 - 1.6 |
|
% |
Expected dividend yield |
|
|
— |
|
|
|
|
— |
|
|
|
|
— |
|
|
Weighted average estimated fair value |
|
$ |
19.27 |
|
|
|
$ |
16.27 |
|
|
|
$ |
9.41 |
|
|
|