Stock-Based Compensation and Stock Options - Stock Compensation Expense for Time Based Options and Performance Based Options (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Effect on basic earnings per share	$ 0.51	$ 0.55	$ 1.94	$ 1.85
Effect on diluted earnings per share	$ 0.50	$ 0.54	$ 1.91	$ 1.83
Time Based Options and Performance Based Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total cost of stock-based compensation included in income before income tax provision	$ 1,143,000	$ 1,023,000	$ 3,566,000	$ 3,110,000
Amount of income tax benefit recognized	(271,000)	(246,000)	(797,000)	(746,000)
Amount charged against net income	$ 872,000	$ 777,000	$ 2,769,000	$ 2,364,000
Effect on basic earnings per share	$ (0.05)	$ (0.04)	$ (0.15)	$ (0.13)
Effect on diluted earnings per share	$ (0.05)	$ (0.04)	$ (0.15)	$ (0.12)
Time Based Options and Performance Based Options [Member] | Cost of Revenues [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total cost of stock-based compensation included in income before income tax provision	$ 529,000	$ 465,000	$ 1,531,000	$ 1,342,000
Time Based Options and Performance Based Options [Member] | General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total cost of stock-based compensation included in income before income tax provision	$ 614,000	$ 558,000	$ 2,035,000	$ 1,768,000