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, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Effect on basic earnings per share	$ 0.64	$ 0.51	$ 1.76	$ 1.94
Effect on diluted earnings per share	$ 0.63	$ 0.50	$ 1.74	$ 1.91
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	$ 1,251,000	$ 1,143,000	$ 3,484,000	$ 3,566,000
Amount of income tax benefit recognized	(231,000)	(271,000)	(724,000)	(797,000)
Amount charged against net income	$ 1,020,000	$ 872,000	$ 2,760,000	$ 2,769,000
Effect on basic earnings per share	$ (0.06)	$ (0.05)	$ (0.15)	$ (0.15)
Effect on diluted earnings per share	$ (0.06)	$ (0.05)	$ (0.15)	$ (0.15)
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	$ 516,000	$ 529,000	$ 1,510,000	$ 1,531,000
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	$ 735,000	$ 614,000	$ 1,974,000	$ 2,035,000