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Stock Based Compensation - Summary of Activity for Outstanding and Exercisable SARs (Detail) - Stock Appreciation Rights (SARs) [Member] - USD ($)
6 Months Ended
Jun. 30, 2017
Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
SARs outstanding 361,799 599,334
SARs exercisable 296,141  
Weighted Average Base Value, SARs outstanding $ 28.52  
Weighted Average Base Value, SARs exercisable $ 27.94  
Weighted Average Remaining Contractual Life, SARs outstanding 3 years 7 months 6 days  
Weighted Average Remaining Contractual Life, SARs exercisable 3 years 3 months 19 days  
Aggregate Intrinsic Value, SARs outstanding $ 14,031  
Aggregate Intrinsic Value, SARs exercisable $ 11,657