Stock-Based Compensation (Tables)
 12 Months Ended
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value
The following table presents details on grants made by the Company for the following periods: 
 
Years Ended
 
Years Ended
 
December 31, 2013
 
December 31, 2012
 
Shares Granted
 
Weighted-
Average Grant
Date Fair Value
 
Shares Granted
 
Weighted-
Average Grant
Date Fair Value
Stock options
1,720,242

 
$
4.16

 
1,339,129

 
$
4.50

RSUs
814,000

 
$
8.47

 
274,070

 
$
6.48
Schedule of Share-Based Compensation, Reserved Shares Outstanding
As of December 31, 2013 and December 31, 2012, the Company had reserved shares of common stock for issuance as follows:
 
December 31, 2013
 
December 31, 2012
Number of stock options outstanding
6,468,743
 
7,426,417
Number of RSUs outstanding
850,351
 
254,863
Shares available for future grant
5,238,699
 
5,001,956
Number of warrants outstanding
912,368
 
912,368
Total shares reserved
13,470,161
 
13,595,604
 
Summary of stock option activity
Option activity for the periods presented is as follows:
 
Options Outstanding
 
Number of
Stock Options
Outstanding
 
Weighted-
Average
Exercise
Price
 
Weighted-
Average
Remaining
Contractual
Life (Years)
 
Aggregate
Intrinsic
Value
(in thousands)
Balance as of December 31, 2010
7,268,909

 
$
1.48

 
6.9
 
$
13,937

Granted
1,570,684

 
7.13

 
 
 
 

Exercised
(368,194
)
 
1.26

 
 
 
2,854

Cancelled
(241,802
)
 
3.28

 
 
 
 

Balance as of December 31, 2011
8,229,597

 
2.52

 
6.6
 
50,541

Granted
1,339,129

 
8.12

 
 
 
 

Exercised
(1,747,213
)
 
1.39

 
 
 
9,558

Cancelled
(395,096
)
 
6.63

 
 
 
 
Balance as of December 31, 2012
7,426,417

 
3.57

 
6.4
 
40,040

Granted
1,720,242

 
7.53

 
 
 
 
Exercised
(2,031,903
)
 
1.31

 
 
 
11,816

Cancelled
(646,013
)
 
7.40

 
 
 
 
Balance as of December 31, 2013
6,468,743

 
$
4.96

 
6.7
 
$
8,991

Exercisable as of December 31, 2013
3,957,414

 
$
3.40

 
5.4
 
$
8,839

Vested and expected to vest as of December 31, 2013
6,028,954

 
$
4.77

 
6.6
 
$
8,983
Summary of restricted stock award activity
Restricted stock award and restricted stock unit ("RSUs") activity for the periods presented is as follows:
 
Number of
Stock RSUs
Outstanding
 
Weighted-Average Grant Date Fair Value
Balance as of December 31, 2011
—

 
$
—

Granted
274,070

 
6.48

Vested
—

 
—

Forfeited
(19,207
)
 
6.49

Balance as of December 31, 2012
254,863

 
6.48

Granted
814,000

 
8.47

Vested
(74,985
)
 
—

Forfeited
(143,527
)
 
8.56

Balance as of December 31, 2013
850,351

 
$
7.99

Vested and expected to vest as of December 31, 2013
695,488

 
 
Schedule of stock-based compensation expense
The Company recognized stock-based compensation expense for awards granted to its employees and nonemployees as follows (in thousands):
 
Years Ended
 
December 31,
 
2013
 
2012
 
2011
Cost of revenue
$
1,453

 
$
1,011

 
$
622

Research and development
1,301

 
872

 
462

Sales and marketing
1,175

 
774

 
770

General and administrative
1,554

 
995

 
588

Total stock-based compensation
$
5,483

 
$
3,652

 
$
2,442
Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan
The following table presents stock-based compensation expense, net of estimated forfeitures, by grant type (in thousands):
 
Years Ended
 
December 31,
 
2013
 
2012
 
2011
Stock options
$
3,906

 
$
3,369

 
$
2,442

Restricted stock awards and restricted stock units (RSUs)
1,577

 
283

 
—

Total stock-based compensation
$
5,483

 
$
3,652

 
$
2,442
Schedule of Unrecognized Compensation Cost, Nonvested Awards
The following table presents unrecognized compensation expense, net of estimated forfeitures, related to the Company’s equity compensation plans as of December 31, 2013, which is expected to be recognized over the following weighted-average periods, (in thousands, except for weighted-average period): 
 
Unrecognized
Compensation
Expense
 
Weighted-
Average Period
(in years)
Stock options
$
7,298

 
2.7
RSUs
$
4,219

 
2.9
Summary of stock option information by exercise price
Additional information regarding options outstanding as of December 31, 2013 is as follows:
 
 
Options Outstanding
 
Options Exercisable
Range of Exercise Prices
 
Options
Outstanding
 
Weighted-Average
Remaining
Contractual
Life (Years)
 
Weighted-Average
Exercise Price
per Share
 
Exercisable
 
Weighted-Average
Exercise Price
per Share
$0.00 - $1.50
 
637,991

 
2.0
 
$
0.58

 
637,991

 
$
0.58

$1.51 - $3.00
 
2,225,689

 
5.2
 
2.18

 
2,168,575

 
2.17

$3.01 - $4.50
 
89,468

 
6.9
 
3.40

 
67,622

 
3.40

$4.51 - $6.00
 
607,140

 
9.8
 
5.55

 
9,564

 
5.34

$6.01 - $7.50
 
1,300,259

 
8.0
 
6.35

 
656,966

 
6.35

$7.51 - $9.00
 
888,200

 
8.5
 
8.76

 
276,590

 
8.84

$9.01 - $11.50
 
629,996

 
8.8
 
9.58

 
87,400

 
9.81

$11.51 - $12.00
 
90,000

 
7.6
 
11.96

 
52,706

 
11.96

 
 
6,468,743

 
6.7
 
$
4.96

 
3,957,414

 
$
3.40
Assumptions for the fair value of stock options
The fair value of the employee stock options were estimated on the grant dates using a Black-Scholes option-pricing model with the following weighted average assumptions:
 
Years Ended
 
December 31,
 
2013
 
2012
 
2011
Expected term (in years)
6.0

 
6.0

 
6.0

Risk-free interest rate
1.4
%
 
1.1
%
 
2.1
%
Expected volatility
59
%
 
60
%
 
57
%
Expected dividend rate
—
%
 
—
%
 
—
%