Income Taxes - Summary of Income Tax Provision (Detail) - USD ($)	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Current — Federal	$ 10,233,000	$ 11,177,000	$ 16,456,000
Current — State	3,121,000	1,905,000	2,834,000
Subtotal	13,354,000	13,082,000	19,290,000
Deferred — Federal	941,000	(955,000)	(1,508,000)
Deferred — State	515,000	81,000	288,000
Subtotal	1,456,000	(874,000)	(1,220,000)
Total	$ 14,810,000	$ 12,208,000	$ 18,070,000