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Stock-Based Compensation - 2015 Long-Term Incentive Plan (Detail) - shares
12 Months Ended
Dec. 31, 2018
Apr. 28, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Common stock, shares reserved for future issuance (in shares) 4,300,000  
2015 Long-Term Incentive Plan    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number of shares authorized (in shares)   4,800,000
Reduction in number of shares available for issuance due to settlement of stock appreciation rights and stock unit or performance unit award (in shares) 2  
Reduction in number of shares available for issuance due to settlement of stock option award (in shares) 1  
Maximum aggregate shares of common stock subject to stock options, appreciation rights, restricted stock or performance stock unit awards (in shares) 1,000,000.0  
Shares available for issuance (in shares) 3,500,000  
Stock options | 2015 Long-Term Incentive Plan    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life (years) 7 years  
Stock options | Minimum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Vesting period 3 years  
Stock options | Maximum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Vesting period 4 years