Stock plans - Stock incentive plans (Details) - USD ($)
|
1 Months Ended |
12 Months Ended |
Jan. 31, 2015 |
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
| Activity under the plan |
|
|
|
|
| Shares available for grant |
|
2,268,938
|
276,805
|
|
| Additional shares reserved |
|
6,253,651
|
25,722,026
|
|
| Balance at the beginning of the period |
1,923,332
|
1,923,332
|
|
|
| Balance at the end of the period |
|
3,659,713
|
1,923,332
|
|
| Restricted stock units |
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|
|
|
| Stock incentive plan |
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|
|
|
| Vesting period |
|
3 years
|
|
|
| Activity under the plan |
|
|
|
|
| Units granted |
|
(493,068)
|
|
|
| Vested and expected to vest |
|
|
|
|
| Weighted-average grant date fair value (in dollars per share) |
|
$ 10.72
|
$ 0.00
|
$ 0.00
|
| Restricted stock units | First anniversary |
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|
|
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| Stock incentive plan |
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|
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| Vesting rate upon anniversaries (as a percent) |
|
33.33%
|
|
|
| Restricted stock units | Second anniversary |
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|
|
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| Stock incentive plan |
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|
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| Vesting rate upon anniversaries (as a percent) |
|
33.33%
|
|
|
| Restricted stock units | Third anniversary |
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|
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| Stock incentive plan |
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|
|
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| Vesting rate upon anniversaries (as a percent) |
|
33.33%
|
|
|
| Stock incentive plans |
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| Stock incentive plan |
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|
|
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| Vesting period |
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4 years
|
|
|
| Vesting rate upon anniversaries (as a percent) |
|
25.00%
|
|
|
| Monthly vesting rate thereafter (as a percent) |
|
2.08%
|
|
|
| Activity under the plan |
|
|
|
|
| Additional shares reserved |
120,452
|
|
4,370,452
|
|
| Stock incentive plans | Minimum |
|
|
|
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| Stock incentive plan |
|
|
|
|
| Employees holding voting rights of all classes of stock (as a percent) |
|
10.00%
|
|
|
| Exercise price of options on common stock (as a percent) |
|
110.00%
|
|
|
| Stock incentive plans | Maximum |
|
|
|
|
| Stock incentive plan |
|
|
|
|
| Term of options granted |
|
10 years
|
|
|
| Stock incentive plans | Options |
|
|
|
|
| Activity under the plan |
|
|
|
|
| Shares available for grant |
|
2,268,938
|
276,805
|
873,233
|
| Additional shares reserved |
|
4,370,452
|
333,333
|
|
| Repurchase of unvested early exercise shares |
|
|
1,959
|
|
| Balance at the beginning of the period |
1,923,332
|
1,923,332
|
1,173,019
|
|
| Options granted (in shares) |
|
2,103,304
|
1,164,990
|
|
| Option cancelled (in shares) |
|
(218,053)
|
(233,270)
|
|
| Options exercised (in shares) |
|
(148,870)
|
(181,407)
|
|
| Balance at the end of the period |
|
3,659,713
|
1,923,332
|
1,173,019
|
| Weighted-average exercise price |
|
|
|
|
| Balance at the beginning of the period (in dollars per share) |
$ 4.37
|
$ 4.37
|
$ 1.40
|
|
| Options granted (in dollars per share) |
|
9.78
|
6.21
|
|
| Options cancelled (in dollars per share) |
|
7.73
|
2.07
|
|
| Options exercised (in dollars per share) |
|
1.98
|
1.15
|
|
| Balance at the end of the period (in dollars per share) |
|
$ 7.38
|
$ 4.37
|
$ 1.40
|
| Additional information |
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|
|
|
| Weighted-average remaining contractual life |
|
8 years 10 months 21 days
|
8 years 10 months 24 days
|
9 years
|
| Aggregate intrinsic value |
|
$ 7,099,000
|
$ 15,946,000
|
$ 2,155,000
|
| Exercisable, Number of shares |
|
833,787
|
|
|
| Exercisable, weighted-average exercise price (in dollars per share) |
|
$ 3.54
|
|
|
| Exercisable, weighted-average remaining contractual life |
|
7 years 6 months 26 days
|
|
|
| Exercisable, aggregate intrinsic value |
|
$ 4,054,000
|
|
|
| Vested and expected to vest |
|
|
|
|
| Number of shares |
|
3,553,680
|
|
|
| Weighted-average exercise price (in dollars per share) |
|
$ 7.33
|
|
|
| Weighted-average remaining contractual life |
|
8 years 10 months 13 days
|
|
|
| Aggregate intrinsic value |
|
$ 7,017,000
|
|
|
| Weighted-average grant date fair value (in dollars per share) |
|
$ 6.26
|
$ 4.68
|
$ 1.83
|
| Fair value of options granted |
|
$ 2,128,000
|
$ 494,000
|
$ 204,000
|
| Exercised, aggregate intrinsic value |
|
$ 1,285,000
|
$ 644,000
|
$ 60,000
|
| Stock incentive plans | Restricted stock units |
|
|
|
|
| Activity under the plan |
|
|
|
|
| Units granted |
|
(493,068)
|
|
|
| ESPP |
|
|
|
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| Stock incentive plan |
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|
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| Purchase price of common stock of the lesser of fair market value on the purchase date or the last trading day preceding the offering date (as a percent) |
85.00%
|
|
|
|
| Activity under the plan |
|
|
|
|
| Additional shares reserved |
325,000
|
325,000
|
|
|
| Vested and expected to vest |
|
|
|
|
| Weighted-average grant date fair value (in dollars per share) |
|
$ 2.17
|
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