Stock-Based Compensation and Stock Options - Stock Compensation Expense for Time Based Options and Performance Based Options (Detail) - USD ($)	3 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Effect on basic earnings per share	$ 0.62	$ 0.47
Effect on diluted earnings per share	$ 0.62	$ 0.46
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	$ 1,179,000	$ 922,000
Amount of income tax benefit recognized	(278,000)	(350,000)
Amount charged against net income	$ 901,000	$ 572,000
Effect on basic earnings per share	$ (0.05)	$ (0.03)
Effect on diluted earnings per share	$ (0.05)	$ (0.03)
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	$ 431,000	$ 483,000
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	$ 748,000	$ 439,000