Income Taxes - Summary of Reconciliation Income Tax Provision from the Statutory Federal Income Tax Rate (Detail) - USD ($)	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income taxes at federal statutory rate	$ 12,427,000	$ 12,749,000	$ 12,918,000
State income taxes, net of federal benefit	3,102,000	2,243,000	2,848,000
Uncertain tax positions	(693,000)	(263,000)	(175,000)
Permanent items and tax credits	(2,018,000)	(1,632,000)	(666,000)
Adjustments to returns as filed	192,000	110,000	131,000
Valuation allowance	(191,000)	127,000	317,000
Impact of tax reform	0	0	(563,000)
Total	$ 12,819,000	$ 13,334,000	$ 14,810,000