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Stock-Based Compensation - Fair Value of Stock Appreciation Rights Estimated, Black-Scholes Option Pricing Model (Detail) - Performance-Based Stock Appreciation Rights [Member]
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Risk-free interest rate, Minimum 0.00% 2.10% 0.00%
Expected life (years)   6 years  
Estimated volatility factor, Minimum 0.00% 59.85% 0.00%
Expected dividends 0.00% 0.00% 0.00%