Share-based Compensation - Computation of Fair Values of Employee Stock Options for Option Grants Issued Under Black-Scholes Option Model (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Dividend yield	1.80%	1.60%
Volatility	57.90%	61.80%
Risk-free interest rate	1.60%	0.60%
Weighted average expected option term (in years)	5 years 7 months 6 days	5 years 6 months 0 days
Weighted average fair value per share of options granted	$ 3.00	$ 2.91