v3.3.1.900
Employee Stock and Benefit Plans (Tables)
12 Months Ended
Dec. 31, 2015
Share-based Compensation [Abstract]  
Stock-based employee compensation
Stock-based compensation for employee stock options is included in the consolidated statements of operations as follows:
 
 
 
Year Ended December 31,
 
 
2015
 
2014
 
2013
 
 
(in thousands)
Cost of revenues
 
$
1,250

 
$
757

 
$
421

Research and development
 
4,936

 
2,463

 
1,038

Sales and marketing
 
3,867

 
2,394

 
1,244

General and administrative
 
6,325

 
4,217

 
1,842

Total stock-based employee compensation
 
$
16,378

 
$
9,831

 
$
4,545

Fair value assumptions of options granted to employees
The fair value of each option granted to employees is estimated on the date of grant using the Black-Scholes option-pricing model based on the following assumptions:

 
 
Year Ended December 31,
 
 
2015
 
2014
 
2013
Expected term (in years)
 
4.9 to 5.9
 
5.3 to 5.9
 
5.4 to 6.1
Volatility
 
45% to 48%
 
48% to 52%
 
52% to 53%
Risk-free interest rate
 
1.3% to 1.7%
 
1.5% to 1.7%
 
0.7% to 1.5%
Dividend yield
 
 
 
Stock option activity
A summary of the Company’s stock option activity is as follows:
 
 
Outstanding
Shares
 
Weighted
Average
Exercise
Price
 
Weighted
Average
Remaining
Contractual
Life (Years)
 
Aggregate
Intrinsic
Value
 
 
 
 
 
 
 
 
(in thousands)
Balance as of December 31, 2012
 
6,513,508

 
$
4.39

 
6.6
 
$
67,711

Granted
 
2,001,400

 
15.78

 
 
 
 
Exercised
 
(952,871
)
 
4.32

 
 
 
 
Canceled
 
(522,944
)
 
10.71

 
 
 
 
Balance as of December 31, 2013
 
7,039,093

 
7.17

 
6.5
 
112,312

Granted
 
2,744,150

 
26.16

 
 
 
 
Exercised
 
(1,216,710
)
 
6.28

 
 
 
 
Canceled
 
(961,126
)
 
16.91

 
 
 
 
Balance as of December 31, 2014
 
7,605,407

 
12.93

 
6.5
 
188,743

Granted
 
1,526,450

 
39.50

 
 
 
 
Exercised
 
(807,846
)
 
12.50

 
 
 
 
Canceled
 
(744,953
)
 
27.67

 
 
 
 
Balance as of December 31, 2015
 
7,579,058

 
16.88

 
5.9
 
131,345

Vested and expected to vest—December 31, 2015
 
7,111,282

 
15.69

 
5.7
 
130,208

Exercisable—December 31, 2015
 
5,195,339

 
9.78

 
4.8
 
121,098

Schedule of exercise price range, outstanding and vested
The following table summarizes the outstanding and vested stock options at December 31, 2015:
 
 
Outstanding
 
Vested
Exercise Price
 
Number of
Shares
 
Weighted
Average
Exercise
Price Per
Share
 
Weighted
Average
Remaining
Contractual
Life (Years)
 
Number of
Shares
 
Weighted
Average
Exercise
Price Per
Share
$1.40 - $1.40
 
156,259

 
$
1.40

 
0.5
 
156,259

 
$
1.40

$1.90 - $1.90
 
940,082

 
1.90

 
1.1
 
940,082

 
1.90

$2.10 - $2.80
 
415,220

 
2.63

 
2.9
 
415,220

 
2.63

$3.80 - $3.80
 
1,117,235

 
3.80

 
3.9
 
1,117,235

 
3.80

$4.10 - $8.90
 
868,867

 
6.16

 
5.4
 
842,958

 
6.08

$9.40 - $16.68
 
786,624

 
13.13

 
6.9
 
606,364

 
12.95

$19.26 - $26.86
 
1,156,772

 
24.00

 
8.1
 
575,066

 
23.69

$30.58 - $30.58
 
827,997

 
30.58

 
8.7
 
423,645

 
30.58

$34.97 - $37.28
 
824,344

 
36.31

 
8.7
 
14,381

 
37.18

$40.68 - $52.14
 
485,658

 
45.13

 
8.9
 
75,635

 
41.39

 
 
7,579,058

 
16.88

 
5.9
 
5,166,845

 
9.79