Fair Value of Option Granted (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Option, Quantitative Disclosures [Line Items]
Risk-free interest rate, minimum	0.55%	0.50%	0.66%
Risk-free interest rate, maximum	1.03%	0.66%	1.83%
Expected dividend yield	0.00%	0.00%	0.00%
Expected option life	4 years	4 years	4 years
Expected volatility, minimum	46.10%	50.40%	47.90%
Expected volatility, maximum	48.40%	50.70%	48.70%
Weighted-average expected volatility	48.20%	50.70%	48.70%