Weighted Average Assumptions Used to Calculate Fair Value of Options Granted (Detail)	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Risk-free interest rate	0.78%	1.47%	2.04%
Expected option life (years)	4 years 3 months 22 days	5 years 2 months 9 days	5 years 3 months 18 days
Expected volatility	56.20%	53.10%	50.90%