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Common Stock (Details) - $ / shares | Nov. 11, 2013 | Aug. 29, 2013 | Dec. 31, 2020 | Dec. 31, 2019
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Class of Stock [Line Items] |  |  |  |
Common stock, shares authorized (in shares) |  |  | 400,000,000 | 400,000,000
Common stock, par value (in dollars per share) |  |  | $ 0.001 | $ 0.001
Outstanding stock options |  |  | 627,317 | 1,611,385
Total common shares reserved for future issuance |  |  | 43,289,612 |
2013 Plan |  |  |  |
Class of Stock [Line Items] |  |  |  |
Shares available for grant under the 2013 Plan |  |  | 29,158,085 |
Total common shares reserved for future issuance | 12,000,000 |  |  |
Award exercise price as percent of fair market value of common stock on grant date threshold | 100.00% |  |  |
Expiration period | 10 years |  |  |
2005 Stock Incentive Plan |  |  |  |
Class of Stock [Line Items] |  |  |  |
Total common shares reserved for future issuance | 3,838,985 |  |  |
2013 Employee Stock Purchase Plan |  |  |  |
Class of Stock [Line Items] |  |  |  |
Total common shares reserved for future issuance |  |  | 8,688,210 |
Maximum employee subscription rate |  | 15.00% |  |
Employee discount on applicable offering period |  | 15.00% |  |
Offering period (no more than 6 months) |  | 6 months |  |
Shares reserved |  | 4,000,000 |  |
Maximum aggregate number of shares to be issued |  | 20,000,000 |  |
RSUs and PSUs |  |  |  |
Class of Stock [Line Items] |  |  |  |
Outstanding RSUs and PSUs |  |  | 4,816,000 | 6,909,530

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- Definition Aggregate number of common shares reserved for future issuance. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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