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Equity Incentive Plans - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands |  | 3 Months Ended | 9 Months Ended |
--- | --- | --- | --- | ---
Feb. 06, 2019 | Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018 | Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |
Shares outstanding awarded |  | 8,099,861 |  | 8,099,861 |  | 5,107,329
Stock-based compensation expense related to vesting of anti-dilution shares |  | $ 5,728 | $ 18,169 | $ 13,957 | $ 20,148 |
Restricted Stock |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |
Stock awards granted |  |  |  | 0 |  |
Weighted-average period of cost expects to recognize |  |  |  | 3 years 1 month 6 days |  |
Unrecognized compensation costs |  | 14,600 |  | $ 14,600 |  |
Stock Options |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |
Expected dividend yield |  |  |  | 0.00% |  |
Weighted-average grant date fair value per share |  |  |  | $ 20.79 |  |
Unrecognized compensation costs |  | 57,800 |  | $ 57,800 |  |
Weighted-average period of cost expects to recognize |  |  |  | 3 years |  |
Stock-Based Compensation Expense |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |
Weighted-average period of cost expects to recognize |  |  |  | 1 year 2 months 12 days |  |
Stock-based compensation expense related to vesting of anti-dilution shares |  | $ 5,700 | $ 18,200 | $ 14,000 | $ 20,100 |
2019 Equity Incentive Plan |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |
Number of share reserved for future issuance | 5,750,000 |  |  |  |  |
Term of awards | 10 years |  |  |  |  |
Percentage of amount increase in outstanding shares | 5.00% |  |  |  |  |
Common stock available for issuance |  | 2,486,308 |  | 2,486,308 |  |
Shares outstanding awarded |  | 3,263,692 |  | 3,263,692 |  |
2019 Employee Stock Purchase Plan |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |
Number of share reserved for future issuance | 700,000 | 700,000 |  | 700,000 |  |
Term of awards | 10 years |  |  |  |  |
Percentage of amount increase in outstanding shares | 1.00% |  |  |  |  |
2019 Employee Stock Purchase Plan | Stock-Based Compensation Expense |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |
Unrecognized compensation costs |  | $ 1,700 |  | $ 1,700 |  |
2019 Employee Stock Purchase Plan | Maximum |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |
Purchase of common stock through payroll deductions, percentage | 20.00% |  |  |  |  |
2017 Equity Incentive Plan |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |
Shares outstanding awarded |  | 4,819,318 |  | 4,819,318 |  |
2017 Equity Incentive Plan | Restricted Stock |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |
Stock awards granted |  |  |  | 635,155 |  |

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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iii) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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