Stockholders' Equity - Stock Repurchase Plan - Additional Information (Detail) - 2016 Stock Incentive Plan - USD ($)	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Feb. 29, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding common stock repurchase program authorized amount (up to)			$ 50,000,000.0
Shares repurchased during period	0	0
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 16,300,000

Number of shares that have been repurchased during the period and are being held in treasury.

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration