Schedule II - Valuation and Qualifying Accounts (Detail) - Allowance for Doubtful Accounts [Member] - USD ($)	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 5,133,000	$ 5,508,000	$ 4,551,000
Additions Charged to Cost and Expenses	2,021,000	1,606,000	1,875,000
Deductions	(3,880,000)	(1,981,000)	(918,000)
Balance at End of Year	$ 3,274,000	$ 5,133,000	$ 5,508,000