Stock-Based Compensation (Detail) - Value of Employee Stock Options on the Date of Grant	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Expected option lives	3.5 years	3.5 years
Expected volatility	42.55%	52.01%
Risk-free interest rate	0.53%	0.59%
Expected dividend yield	0.00%	5.51%