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Stock-Based Compensation (PSUs, RSUs and Restricted Stock) - Additional Information (Detail) - USD ($)
shares in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2017
Mar. 31, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
PSU shares grant approved by board of directors       520  
Compensation expense recognized $ 1,856,000   $ 1,551,000 $ 3,739,000 $ 3,109,000
Performance Stock Units (PSUs) [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
PSU shares grant approved by board of directors   500      
Market-Based PSUs, RSUs and Restricted Stock [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Unrecognized compensation expense related to other than options 7,900,000     $ 7,900,000  
Recognition period of unvested compensation expense       3 years  
Performance-Based PSUs [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Unrecognized compensation expense related to other than options 11,500,000     $ 11,500,000  
Recognition period of unvested compensation expense       3 years  
Performance-Based PSU Awards [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Compensation expense recognized $ 0     $ 0