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Stock-Based Compensation - SAR Activity (Detail) - Stock Appreciation Rights [Member] - USD ($)
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Schedule Of Stock Appreciation Rights Activity [Line Items]      
SARs Outstanding, Beginning Balance 515,830 739,194 1,374,380
Granted, SARs 15,585 3,866 121,176
Exercised, SARs (263,626) (218,826) (749,334)
Canceled, SARs (5,712) (8,404) (7,028)
Shares Outstanding, SARs, Ending Balance 262,077 515,830 739,194
Outstanding, Weighted Average Grant Price Per Share, Beginning Balance $ 13.98 $ 12.93 $ 9.28
Vested, SARs 229,415    
Granted, Weighted Average Grant Price Per Share $ 41.19 37.88 21.95
Exercisable, SARs 229,415    
Exercised, Weighted Average Grant Price Per Share $ 13.86 10.96 7.70
Canceled, Weighted Average Grant Price Per Share 21.94 4.74 13.10
Outstanding, Weighted Average Grant Price Per Share, Ending Balance 13.13 $ 13.98 $ 12.93
Vested, Weighted Average Grant Price Per Share 13.34    
Exercisable, Weighted Average Grant Price Per Share $ 13.34    
Weighted Average Remaining Contractual Life, Outstanding 5 years 8 months 12 days    
Weighted Average Remaining Contractual Life, Vested 5 years 3 months 18 days    
Weighted Average Remaining Contractual Life, Exercisable 5 years 3 months 18 days    
Aggregate Intrinsic Value, Outstanding $ 5,948,519    
Aggregate Intrinsic Value, Vested 5,670,343    
Aggregate Intrinsic Value, Exercisable $ 5,670,343