Pension Plans - Schedule of Net Pension Costs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan Net Periodic Benefit Cost [Abstract]
Employer service cost	$ 2,447	$ 1,828	$ 1,574
Interest cost	126	131	153
Expected return on plan assets	(243)	(130)	(131)
Amortization of prior service credit	58	(23)	(14)
Amortization of net loss		216	154
Net pension cost	$ 2,388	$ 2,022	$ 1,736