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Summary of Weighted Average Valuation Inputs (Detail) - Stock Options And Stock Appreciation Rights
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected term 4 years 1 month 6 days 4 years 2 months 12 days 4 years 1 month 6 days
Expected volatility 24.60% 25.80% 27.20%
Expected dividend yield 0.00% 0.00% 0.00%
Risk-free interest rate 1.50% 1.50% 0.70%