Weighted Average Assumptions Used to Calculate Fair Value of Options Granted (Detail) - Stock Options	3 Months Ended		6 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Risk-free interest rate	1.63%	1.75%	1.59%	1.60%
Expected option life (years)	4 years 1 month 17 days	4 years 2 months 9 days	4 years 1 month 21 days	4 years 2 months 9 days
Expected volatility	48.30%	48.70%	49.70%	49.30%