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Stock-Based Awards - Summary of Unrecognized Stock-Based Compensation Expense and Average Remaining Vesting Period (Detail) - Employees and Directors [Member]
$ in Thousands
6 Months Ended
Jun. 30, 2019
USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Average Remaining Vesting Period 2 years 1 month 28 days
Unrecognized Stock-Based Compensation $ 21,078