Equity Incentive Plans and Stock Based Compensation (Tables)
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12 Months Ended |
Dec. 31, 2015 |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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Stock Option Activity Under Equity Incentive Plan |
Activity under the 2004 and 2014 Plans is set forth below:
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Weighted
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Shares
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Outstanding Options
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Average
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Available
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Number of
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Exercise
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Exercise
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for Grant
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Shares
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Price
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Price
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Balances, December 31, 2012
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498,411
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5,098,972
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$
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0.42–7.75
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$
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3.18
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Additional shares reserved
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1,250,000
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—
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Options granted
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(1,663,500
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)
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1,663,500
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4.45–5.58
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5.10
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Options exercised
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—
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(145,641
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)
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0.79–3.46
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1.56
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Options canceled
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90,325
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(90,325
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)
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1.44–7.75
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6.49
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Balances, December 31, 2013
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175,236
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6,526,506
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$
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0.42–7.75
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$
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3.66
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Additional shares reserved
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7,250,000
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—
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Shares expired
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(1,286,025
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)
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—
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Options granted
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(1,895,250
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)
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1,895,250
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2.91–4.99
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3.78
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Options exercised
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—
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(73,282
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)
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0.64–4.90
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1.43
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Options canceled
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179,532
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(179,532
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)
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1.64–6.18
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4.63
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Balances, December 31, 2014
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4,423,493
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8,168,942
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$
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0.42–7.75
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$
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3.69
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Additional shares reserved
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—
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—
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Options granted
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(2,290,500
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)
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2,290,500
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0.48-5.06
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4.36
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Options exercised
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—
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(99,759
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)
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0.79-4.90
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1.75
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Options canceled
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1,327,547
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(1,327,547
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)
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1.30-7.75
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4.39
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Balances, December 31, 2015
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3,460,540
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9,032,136
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$
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0.42–7.75
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$
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3.77
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Stock Options Outstanding and Exercisable by Exercise Price |
At December 31, 2015, stock options outstanding and exercisable by exercise price were as follows:
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Options Outstanding
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Options Exercisable
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Range of
Exercise
Prices
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Number
Outstanding
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Weighted
Average
Remaining
Contractual
Life (Years)
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Weighted
Average
Exercise
Price
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Number
Exercisable
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Weighted
Average
Exercise
Price
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$0.42-$1.38
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534,650
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2.20
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$
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1.10
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522,650
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$
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1.11
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$1.44-$1.44
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1,331,064
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4.01
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$
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1.44
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1,331,064
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$
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1.44
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$1.49-$3.46
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1,428,718
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4.49
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$
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1.97
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1,397,258
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$
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1.94
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$3.62-$3.62
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1,164,013
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7.37
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$
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3.62
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641,099
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$
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3.62
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$3.87-$5.06
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2,011,782
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8.03
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$
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4.46
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766,498
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$
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4.52
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$5.09-$7.75
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2,561,909
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5.50
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$
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6.09
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2,225,216
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$
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6.17
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$0.42-$7.75
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9,032,136
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5.79
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$
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3.77
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6,883,785
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$
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3.59
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Stock-Based Compensation Expense |
Stock-based compensation expense, which consists of the compensation cost for employee stock options and ESPP, and the value of options issued to non-employees for services rendered, was allocated to research and development and general and administrative in the consolidated statements of operations as follows (in thousands):
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Years Ended December 31,
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2015
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2014
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2013
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Stock-based compensation expense:
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Research and development
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$
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4,090
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$
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3,123
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$
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2,562
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General and administrative
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2,711
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2,365
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2,360
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$
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6,801
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$
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5,488
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$
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4,922
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Weighted-Average Fair Value Valuation Assumptions |
The fair value of employee stock options and employee purchase rights under the Company’s 2004 Purchase Plan was estimated using the following weighted-average assumptions for the years ended December 31, 2015, 2014 and 2013:
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Years Ended December 31,
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2015
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2014
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2013
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Employee Stock Options
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Risk-free interest rate
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1.70
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%
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1.83
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%
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1.14
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%
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Expected life (in years)
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5.99
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5.98
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5.97
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Dividend yield
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—
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—
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—
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Volatility
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83
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%
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94
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%
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101
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%
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Weighted-average fair value of stock options granted
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$
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3.06
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$
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2.89
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$
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4.04
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Employee Stock Purchase Plan
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Risk-free interest rate
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0.39
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%
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0.20
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%
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0.19
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%
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Expected life (in years)
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1.24
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1.24
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1.25
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Dividend yield
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—
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—
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—
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Volatility
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50
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%
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49
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%
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77
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%
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Weighted-average fair value of ESPP purchase rights
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$
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1.58
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$
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1.60
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$
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2.27
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Non-employee Stock-based Compensation Expense |
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Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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Weighted-Average Fair Value Valuation Assumptions |
The fair value of the stock options granted were revalued at each reporting date using the Black-Scholes valuation model as prescribed by ASC 505-50 Equity-Based Payments to Non-Employees using the following assumptions:
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Years Ended December 31,
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2015
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2014
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2013
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Risk-free interest rate
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2.14
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%
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2.52
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%
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2.51
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%
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Expected life (in years)
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10
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10
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10
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Dividend yield
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—
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—
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—
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Expected volatility
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103
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%
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97
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%
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100
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%
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