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Stock-based Compensation (Tables) | 12 Months Ended
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Dec. 29, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract] |
Schedule of Allocated Employee Stock-Based Compensation Expense | The allocation of stock-based compensation for our equity incentive plans and our Employee Stock Purchase Plan (the “ESPP”) was as follows (in thousands):
| Year Ended December 31,
| 2017 |  | 2016 |  | 2015
Research and development | $ | 7,569 |  |  | $ | 9,366 |  |  | $ | 11,691 |
Selling, general and administrative | 16,369 |  |  | 13,546 |  |  | 10,286 |
Total stock-based compensation | $ | 23,938 |  |  | $ | 22,912 |  |  | $ | 21,977 |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value | The weighted average grant-date fair value of our stock option grants and ESPP purchases were as follows:
| Year Ended December 31,
| 2017 |  | 2016 |  | 2015
Stock options | $ | 11.42 |  |  | $ | 4.77 |  |  | $ | 2.55 |
ESPP | $ | 6.00 |  |  | $ | 2.17 |  |  | $ | 1.20 |
Schedule of Fair Value of Employee Share-Based Payments Awards Stock Option Assumptions and Weighted Average Fair Values | The grant-date fair value of employee stock option grants and ESPP purchases was estimated using the following assumptions:
| Year Ended December 31,
| 2017 |  | 2016 |  | 2015
Stock options: |  |  |  |  |
Risk-free interest rate | 1.98 | % |  | 1.15 | % |  | 1.22 | %
Dividend yield | — | % |  | — | % |  | — | %
Volatility | 59 | % |  | 76 | % |  | 93 | %
Expected life | 4.5 years |  |  | 4.4 years |  |  | 4.5 years |
ESPP: |  |  |  |  |
Risk-free interest rate | 1.09 | % |  | 0.55 | % |  | 0.15 | %
Dividend yield | — | % |  | — | % |  | — | %
Volatility | 58 | % |  | 65 | % |  | 98 | %
Expected life | 6 months |  |  | 6 months |  |  | 6 months |
Schedule of Fair Value of Employee Share-Based Payments Awards ESPP Assumptions and Weighted Average Fair Values | The grant-date fair value of employee stock option grants and ESPP purchases was estimated using the following assumptions:
| Year Ended December 31,
| 2017 |  | 2016 |  | 2015
Stock options: |  |  |  |  |
Risk-free interest rate | 1.98 | % |  | 1.15 | % |  | 1.22 | %
Dividend yield | — | % |  | — | % |  | — | %
Volatility | 59 | % |  | 76 | % |  | 93 | %
Expected life | 4.5 years |  |  | 4.4 years |  |  | 4.5 years |
ESPP: |  |  |  |  |
Risk-free interest rate | 1.09 | % |  | 0.55 | % |  | 0.15 | %
Dividend yield | — | % |  | — | % |  | — | %
Volatility | 58 | % |  | 65 | % |  | 98 | %
Expected life | 6 months |  |  | 6 months |  |  | 6 months |
Summary of All Stock Option Activity | Stock option activity for the year ended December 31, 2017 was as follows (dollars in thousands, except per share amounts):
| Shares |  | Weighted Average Exercise Price |  | Weighted Average Remaining Contractual Term |  | Aggregate Intrinsic Value
Options outstanding at December 31, 2016 | 24,999,665 |  |  | $ | 4.91 |  |  |  |  |
Granted | 2,166,110 |  |  | $ | 23.43 |  |  |  |  |
Exercised | (4,469,203 | ) |  | $ | 3.91 |  |  |  |  |
Forfeited | (229,793 | ) |  | $ | 8.09 |  |  |  |  |
Expired | (258,333 | ) |  | $ | 9.91 |  |  |  |  |
Options outstanding at December 31, 2017 | 22,208,446 |  |  | $ | 6.83 |  |  | 4.05 years |  | $ | 523,448 |
Exercisable at December 31, 2017 | 16,158,740 |  |  | $ | 4.51 |  |  | 3.46 years |  | $ | 418,304 |
Summary of All RSU Activity | A summary of all RSU activity were as follows (dollars in thousands, except per share amounts):
| Shares |  | Weighted Average Grant Date Fair Value |  | Weighted Average Remaining Contractual Term |  | Aggregate Intrinsic Value
Awards outstanding at December 31, 2016 | 2,469,791 |  |  | $ | 8.69 |  |  |  |  |
Awarded | 2,137,817 |  |  | $ | 24.60 |  |  |  |  |
Vested and released | (708,541 | ) |  | $ | 7.97 |  |  |  |  |
Forfeited | (136,077 | ) |  | $ | 11.48 |  |  |  |  |
Awards outstanding at December 31, 2017 | 3,762,990 |  |  | $ | 17.76 |  |  | 1.95 years |  | $ | 114,395 |

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- Definition Tabular disclosure for stock option plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of employee stock purchase plans, including, but not limited to: (a) expected term, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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