Rendering

Component: (Network and Table)
Network
2306301 - Disclosure - Equity Award Plans (Tables)
(http://www.a10networks.com/role/EquityAwardPlansTables)
Table(Implied)
Slicers (applies to each fact value in each table cell)
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]Period [Axis]
2016-01-01 - 2016-12-31
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
 
Summary of Stock-based Compensation
A summary of our stock-based compensation expense is as follows (in thousands):
 
Years Ended December 31,
 
2016
 
2015
 
2014
Stock-based compensation by type of award:
 
 
 
 
 
Stock options
$
4,153

 
$
5,565

 
$
5,852

Restricted stock units
12,567

 
8,871

 
3,217

Employee stock purchase rights
202

 
2,425

 
3,290

 
$
16,922

 
$
16,861

 
$
12,359

 
 
 
 
 
 
Stock-based compensation by category of expense:
 
 
 
 
 
Cost of revenue
$
1,105

 
$
1,533

 
$
1,063

Sales and marketing
7,006

 
7,735

 
5,829

Research and development
5,732

 
5,437

 
3,932

General and administrative
3,079

 
2,156

 
1,535

 
$
16,922

 
$
16,861

 
$
12,359

 
 
ESPP Valuation Assumptions
The fair values of the options and employee stock purchase rights are estimated as of the grant date using the Black-Scholes option-pricing model with the following assumptions: 

 
Options
 
Employee Stock Purchase Rights
 
Years Ended December 31,
 
Years Ended December 31,
 
2016
 
2015
 
2014
 
2016
 
2015
 
2014
Expected term (in years)
4.9
 
4.8
 
4.8
 
1.3
 
1.3
 
1.3
Risk-free interest rate
1.4%
 
1.6%
 
1.8%
 
0.8%
 
0.5%
 
0.3%
Expected volatility
49%
 
50%
 
41%
 
42%
 
41%
 
27%
Dividend rate
—%
 
—%
 
—%
 
—%
 
—%
 
—%
 
 
Stock Options Valuation Assumptions
The fair values of the options and employee stock purchase rights are estimated as of the grant date using the Black-Scholes option-pricing model with the following assumptions: 

 
Options
 
Employee Stock Purchase Rights
 
Years Ended December 31,
 
Years Ended December 31,
 
2016
 
2015
 
2014
 
2016
 
2015
 
2014
Expected term (in years)
4.9
 
4.8
 
4.8
 
1.3
 
1.3
 
1.3
Risk-free interest rate
1.4%
 
1.6%
 
1.8%
 
0.8%
 
0.5%
 
0.3%
Expected volatility
49%
 
50%
 
41%
 
42%
 
41%
 
27%
Dividend rate
—%
 
—%
 
—%
 
—%
 
—%
 
—%
 
 
Summary of Activity under Stock Option Plans
The following table summarizes our stock option activities and related information:

 
 
Number of Shares
(thousands)
 
Weighted-Average Exercise Price
 
Weighted-Average Remaining Contractual Term
(Years)
 
Aggregate Intrinsic Value
(thousands)
Outstanding as of December 31, 2015
 
9,291

 
$
4.78

 
 
 
 
Granted
 
672

 
$
5.52

 
 
 
 
Exercised
 
(1,444
)
 
$
4.22

 
 
 
 
Canceled (1)
 
(651
)
 
$
6.23

 
 
 
 

Outstanding as of December 31, 2016
 
7,868

 
$
4.82

 
6.2
 
$
28,931

Vested and expected to vest as of December 31, 2016
 
7,758

 
$
4.82

 
6.2
 
$
28,554

Vested and exercisable as of December 31, 2016
 
5,688

 
$
4.57

 
5.6
 
$
22,363


_____________________________________
(1) Common shares subject to awards granted under the 2008 Plan and canceled after March 21, 2014 are reallocated to the 2014 Plan’s share reserve and become available for issuance under the 2014 Plan. During the years ended 2016 and 2015, 266,799 shares and 1,640,324 shares of the canceled stock options, respectively, were reallocated and became available for issuance under the 2014 Plan.
 
 
Stock Option Information
The following table provides information pertaining to our stock options (in thousands, except weighted-average fair values):
 
Years Ended December 31,
 
2016
 
2015
 
2014
Fair value of options granted
$
1,603

 
$
869

 
$
11,683

Weighted-average fair value of options granted
$
2.38

 
$
2.13

 
$
2.79

Intrinsic value of options exercised
$
5,990

 
$
2,299

 
$
14,863

 
 
Summary of Restricted Stock Units Activity
The following table summarizes our stock award activities and related information:
 
Number of Shares
(thousands)
 
Weighted Average Grant Date Fair Value
 
Weighted-Average Remaining Vesting Term (Years)
 
Aggregate Intrinsic Value
(thousands)
Outstanding as of December 31, 2015
3,452

 
$
5.88

 
 
 
 
Granted
4,550

 
$
6.50

 
 
 
 
Released
(1,139
)
 
$
8.16

 
 
 
 
Canceled
(904
)
 
$
6.56

 
 
 
 
Outstanding as of December 31, 2016
5,959

 
$
5.81

 
1.6
 
$
49,517