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Stock-Based Compensation - Additional Information (Detail) - Restricted Stock Units (RSUs) [Member]
3 Months Ended
Mar. 31, 2019
USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Total compensation cost related to RSU's not yet recognized $ 36,742,000
Weighted average number of years for recognition of outstanding nonvested RSUs 1 year 10 months 2 days