Stockholders' Equity - Additional Information (Detail) - USD ($)				12 Months Ended
	Jun. 26, 2018	Apr. 03, 2018	Oct. 24, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Proceeds from sale of common stock			$ 189,700,000
Stock issued during period subject to lock-up and stand-still provisions period		5 years
Number of shares to be issued upon exercise of outstanding options or vesting of RSUs				19,250,000
Number of shares available for issuance under equity compensation plans				12,690,000
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				$ 6,000
Compensation expense in connection with 401(k) retirement plan				$ 2,800,000	$ 1,600,000	$ 1,100,000
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
Number of additional shares available for award grants	10,900,000
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] | Shares of Common Stock Underlying Outstanding 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] | Shares of Common Stock Underlying Outstanding 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
2017 Performance Incentive Plan [Member] | Restricted Stock Units (RSU) [Member] | Director [Member]
Class of Stock [Line Items]
Service period for stock-based compensation award granted				1 year
Common Shares [Member]
Class of Stock [Line Items]
Sale of common stock, Shares		8,284,600	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				31,940,416