| Schedule of stock-based compensation expense related to all of the entity's share-based awards |
Total stock‑based compensation expense related to all of our stock‑based awards was as follows (in thousands):
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Year Ended December 31,
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2015
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2014
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2013
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Research and development
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$
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4,100
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$
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4,674
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$
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3,930
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General and administrative
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3,303
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5,113
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2,997
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Restructuring charges
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—
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—
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239
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Total stock-based compensation expense
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$
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7,403
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$
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9,787
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$
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7,166
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| Schedule of option activity under equity incentive plans |
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Weighted-
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Average
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Remaining
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Shares Available
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Number of Shares
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Weighted-Average
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Contractual Term
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Aggregate
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For Grant
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Underlying Options
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Exercise Price
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(in years)
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Intrinsic Value
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Outstanding at January 1, 2013
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3,198,586
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13,604,377
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$
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11.52
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Authorized for grant
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7,775,000
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—
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Granted
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(3,140,956)
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3,140,956
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$
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5.46
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Exercised
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—
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—
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$
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—
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Cancelled
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1,213,131
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(1,213,131)
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$
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8.26
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Outstanding at December 31, 2013
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9,045,761
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15,532,202
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$
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10.55
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Authorized for grant
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—
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—
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Granted
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(3,467,120)
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3,467,120
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$
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3.39
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Exercised
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—
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(11,219)
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$
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3.44
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Cancelled
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2,017,430
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(2,017,430)
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$
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10.75
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Outstanding at December 31, 2014
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7,596,071
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16,970,673
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$
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9.07
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Authorized for grant
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—
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—
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Granted
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(3,875,170)
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3,875,170
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$
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2.28
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Exercised
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—
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(214,295)
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$
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2.75
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Cancelled
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1,525,076
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(1,525,076)
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$
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17.56
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Outstanding at December 31, 2015
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5,245,977
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19,106,472
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$
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7.08
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5.85
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$
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3,053,499
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Vested and expected to vest at December 31, 2015
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18,958,691
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$
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7.12
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Exercisable at December 31, 2015
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15,089,131
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$
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8.24
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5.08
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$
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865,450
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Exercisable at December 31, 2014
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14,243,893
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$
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10.09
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Exercisable at December 31, 2013
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13,246,612
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$
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11.44
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| Schedule of stock options by exercise price |
Details of our stock options by exercise price are as follows as of December 31, 2015:
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Options Outstanding
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Options Exercisable
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Number of
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Weighted-Average
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Outstanding
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Remaining
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Weighted-Average
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Number of
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Weighted-Average
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Exercise Price
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Options
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Contractual Life (in years)
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Exercise Price
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Options
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Exercise Price
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$1.68 - $2.14
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3,398,170
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8.99
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$
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2.14
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965,799
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$
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2.14
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$2.72 - $3.59
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3,818,711
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7.99
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3.43
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2,419,487
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3.40
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$3.64 - $6.51
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3,613,435
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5.53
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6.31
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3,432,883
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6.37
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$6.55 - $7.40
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2,490,644
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4.24
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6.81
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2,490,644
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6.81
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$7.53 - $9.62
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3,392,461
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4.83
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8.70
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3,387,320
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8.70
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$9.74 - $26.45
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2,393,051
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1.58
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19.11
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2,392,999
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19.11
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$1.68 - $26.45
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19,106,472
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5.85
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7.08
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15,089,132
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8.24
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