Schedule of Stock Options Weighted Average Contractual Terms (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award
Outstanding	5 years 8 months 12 days	6 years 4 months 24 days	2 years 3 months 18 days
Vested and Expected to vest	5 years 7 months 6 days	6 years 2 months 12 days	5 years 4 months 24 days
Exercisable	4 years 10 months 24 days	4 years	1 year 8 months 12 days