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, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Net Income per Basic Common Share	$ 1.06	$ 0.98	$ 0.84	$ 0.95	$ 1.11	$ 0.78	$ 0.90	$ 0.94	$ 3.83	$ 3.74	$ 2.59
Net Income per Diluted Common Share	$ 1.04	$ 0.96	$ 0.83	$ 0.94	$ 1.09	$ 0.76	$ 0.88	$ 0.92	$ 3.77	$ 3.66	$ 2.55
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									$ 5,559,000	$ 5,198,000	$ 4,978,000
Amount of income tax benefit recognized									1,210,000	1,119,000	1,057,000
Amount charged to net income									$ 4,349,000	$ 4,079,000	$ 3,921,000
Net Income per Basic Common Share									$ 0.25	$ 0.23	$ 0.22
Net Income per Diluted Common Share									$ 0.25	$ 0.23	$ 0.22
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									$ 2,566,000	$ 2,063,000	$ 2,020,000
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									$ 2,993,000	$ 3,135,000	$ 2,958,000