Weighted Average Assumptions Used to Calculate Fair Value of Options Granted (Detail)	3 Months Ended		6 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Risk-free interest rate	1.39%	0.68%	0.85%	1.72%
Expected option life (years)	4 years 2 months 23 days	4 years 2 months 12 days	4 years 3 months 4 days	5 years 3 months 15 days
Expected volatility	50.60%	56.20%	51.90%	51.80%