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Stockholders' Equity - Additional Information (Detail) - USD ($) |  | 12 Months Ended
--- | --- | ---
Oct. 24, 2016 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Class of Stock [Line Items] |  |  |  |
Preferred stock, shares authorized |  | 10,000,000 | 10,000,000 |
Preferred stock, par value |  | $ 0.0001 | $ 0.0001 |
Preferred stock, shares designated |  | 0 | 0 |
Preferred stock, shares issued |  | 0 | 0 |
Preferred stock, shares outstanding |  | 0 | 0 |
Proceeds from sale of common stock | $ 189,700,000 |  |  |
Common stock, shares authorized |  | 300,000,000 | 300,000,000 |
Maximum 401(k) per employee, percentage of annual salary |  | 60.00% |  |
Matching 401(k) employer contribution, maximum amount |  | $ 4,000 |  |
Compensation expense in connection with 401(k) retirement plan |  | $ 1,600,000 | $ 1,100,000 | $ 900,000
Change in control severance payment period for executives |  | 12 months |  |
Change in control severance payment period for employees |  | 6 months |  |
Change in control cash severance payment for chief executive officer |  | 24 months base salary plus annual target incentive pay |  |
Employee Stock Purchase Plan [Member] |  |  |  |
Class of Stock [Line Items] |  |  |  |
Common stock, shares authorized |  | 2,500,000 |  |
Percentage of purchase price of stock |  | 85.00% |  |
2017 Performance Incentive Plan [Member] |  |  |  |
Class of Stock [Line Items] |  |  |  |
Number of common stock shares available for stock options grants |  | 8,300,000 |  |
Share-based compensation plan's share limit reduction for every one restricted stock unit granted |  | 1.5 |  |
Stock options term under equity incentive plans |  | 8 years |  |
2017 Performance Incentive Plan [Member] | Director [Member] |  |  |  |
Class of Stock [Line Items] |  |  |  |
Service period for stock-based compensation award granted |  | 1 year |  |
2017 Performance Incentive Plan [Member] | Stock Options [Member] | Employee [Member] |  |  |  |
Class of Stock [Line Items] |  |  |  |
Service period for stock-based compensation award granted |  | 4 years |  |
2017 Performance Incentive Plan [Member] | Stock Options [Member] | Director [Member] |  |  |  |
Class of Stock [Line Items] |  |  |  |
Service period for stock-based compensation award granted |  | 1 year |  |
2017 Performance Incentive Plan [Member] | Restricted Stock Units (RSU) [Member] | Employee [Member] |  |  |  |
Class of Stock [Line Items] |  |  |  |
Service period for stock-based compensation award granted |  | 3 years |  |
Common Shares [Member] |  |  |  |
Class of Stock [Line Items] |  |  |  |
Sale of common stock, Shares | 14,950,000 |  | 14,950,000 |
Underwriting commissions and discounts | $ 12,100,000 |  |  |
Legal, accounting fees, filing fees and other offering expenses | $ 400,000 |  |  |
Common stock, shares reserved for issuance in equity compensation plans |  | 26,761,122 |  |

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