Stock Options and Stock-Based Compensation - Stock Compensation Expense for Time Based Options and Performance Based Options (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Basic	$ 1.13	$ 1	$ 1.16	$ 1.16	$ 1.06	$ 0.98	$ 0.84	$ 0.95	$ 4.45	$ 3.83	$ 3.74
Diluted	$ 1.12	$ 0.99	$ 1.15	$ 1.14	$ 1.04	$ 0.96	$ 0.83	$ 0.94	$ 4.4	$ 3.77	$ 3.66
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 taxes									$ 4,982,000	$ 5,559,000	$ 5,198,000
Amount of income tax benefit recognized									(987,000)	(1,210,000)	(1,119,000)
Amount charged to net income									$ 3,995,000	$ 4,349,000	$ 4,079,000
Basic									$ 0.23	$ 0.25	$ 0.23
Diluted									$ 0.23	$ 0.25	$ 0.23
Time Based Options and Performance Based Options [Member] | Cost of Revenue [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 taxes									$ 2,797,000	$ 2,566,000	$ 2,063,000
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 taxes									$ 2,185,000	$ 2,993,000	$ 3,135,000