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Significant Accounting Policies - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2017 | Sep. 30, 2017
Summary Of Significant Accounting Policies [Line Items] |  |
Cash and cash equivalents maturity period, maximum |  | 90 days
Income tax expense | $ 248 | $ 1,338
ASU 2016-09 [Member] |  |
Summary Of Significant Accounting Policies [Line Items] |  |
Income tax expense | $ 248 | $ 1,338
Decrease in earnings per share basic |  | $ 0.01

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