Stock-Based Compensation (Detail) - Weighted-Average Assumptions Used To Determine Fair Value Of SARs Grants On Date Of Grant Using Black-Scholes-Merton Valuation Model - Stock Appreciation Rights (SARs)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%	0.00%
Expected stock price volatility	22.00%	24.00%	25.00%
Risk-free interest rate	1.10%	1.50%	1.30%
Expected life in years	4 years 4 months 21 days	4 years 4 months 28 days	4 years 5 months 5 days