Weighted Average Assumptions Used to Calculate Fair Value of Options Granted (Detail)	3 Months Ended		6 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Risk-free interest rate	1.75%	1.39%	1.60%	0.85%
Expected option life (years)	4 years 2 months 9 days	4 years 2 months 23 days	4 years 2 months 9 days	4 years 3 months 4 days
Expected volatility	48.70%	50.60%	49.30%	51.90%