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Employee Benefits - Additional Information (Detail) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018 | Dec. 31, 2018 | Dec. 31, 2017
Retirement Benefits [Abstract] |  |  |  |  |  |
Maximum contribution percentage by employee |  |  | 90.00% |  | 90.00% |
Discretionary contribution by employer | $ 28 | $ 13 | $ 55 | $ 25 | $ 57 | $ 62

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- References No definition available. + Details
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- Definition Amount of discretionary contributions made by an employer to a defined contribution plan. + References No definition available. + Details
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- Definition Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan. + References No definition available. + Details
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