Equity Incentive Plans and Stock Based Compensation (Tables)
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12 Months Ended |
Dec. 31, 2016 |
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, 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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Additional shares reserved
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—
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—
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Options granted
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(3,072,500
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)
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3,072,500
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0.38-0.55
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0.53
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Options exercised
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(6,187
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)
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0.48-0.55
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0.53
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Options canceled
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1,156,704
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(1,156,704
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)
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0.42-5.09
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2.50
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Balances, December 31, 2016
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1,544,744
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10,941,745
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$
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0.42–7.75
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$
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3.00
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Stock Options Outstanding and Exercisable by Exercise Price |
At December 31, 2016, 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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$0.38-$0.53
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1,153,000
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9.29
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$
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0.49
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265,717
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$
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0.49
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$0.55-$0.55
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1,414,999
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8.86
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$
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0.55
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315,934
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$
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0.55
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$0.79-$1.44
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1,769,313
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2.47
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$
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1.35
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1,769,313
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$
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1.35
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$1.49-$3.62
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2,472,416
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4.55
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$
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2.67
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2,225,880
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$
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2.57
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$3.87-$4.43
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1,430,358
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6.99
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$
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4.36
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849,104
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$
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4.33
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$4.45-$7.75
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2,701,659
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3.93
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$
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6.00
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2,650,117
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$
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6.02
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$0.38-$7.75
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10,941,745
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5.44
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$
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3.00
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8,076,065
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$
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3.47
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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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2016
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2015
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2014
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Stock-based compensation expense:
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Research and development
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$
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1,281
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$
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4,090
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$
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3,123
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General and administrative
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1,808
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2,711
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2,365
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$
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3,089
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$
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6,801
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$
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5,488
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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, 2016, 2015 and 2014:
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Years Ended December 31,
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2016
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2015
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2014
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Employee Stock Options
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Risk-free interest rate
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1.60
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%
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1.70
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%
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1.83
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%
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Expected life (in years)
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5.97
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5.99
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5.98
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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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108
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%
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83
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%
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94
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%
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Weighted-average fair value of stock options granted
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$
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0.44
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$
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3.06
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$
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2.89
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Employee Stock Purchase Plan
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Risk-free interest rate
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0.56
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%
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0.39
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%
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0.20
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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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1.24
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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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161
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%
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50
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%
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49
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%
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Weighted-average fair value of ESPP purchase rights
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$
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0.22
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$
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1.58
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$
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1.60
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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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2016
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2015
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2014
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Risk-free interest rate
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1.70
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%
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2.14
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%
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2.52
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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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111
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%
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103
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%
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97
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%
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