Stock Based Compensation (Detail) - The weighted average for key assumptions used in determining the fair value of options	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Expected price volatility	53.25%	45.89%	53.21%
Risk-free interest rate	0.91%	1.34%	2.30%
Weighted average expected life in years	5 years 6 months	5 years 255 days	5 years 219 days
Forfeiture rate	21.87%	19.82%	14.27%