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Stock-Based Compensation - Summary of Assumptions Used to Estimate Fair Value of Each SAR (Detail) (USD $)
6 Months Ended
Jun. 30, 2014
Jun. 30, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]    
Weighted-average fair value of grants $ 18.52 $ 11.68
Dividend yield 0.00% 0.00%
Average risk-free interest rate 1.80% 0.70%
Expected term (years) 5 years 5 years
Expected volatility 54.00% 64.00%