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Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Compensation And Retirement Disclosure [Abstract]
Maximum Percentage of employee earnings the employer contributes as a matching contribution in 401(k) plan	4.00%
Employer matching contributions, amount	$ 1.1	$ 0.7	$ 0.2

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No definition available.

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- Definition

Amount of discretionary contributions made by an employer to a defined contribution plan.

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No definition available.

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- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

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No definition available.

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