Consolidated Statements of Comprehensive Earnings - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net Earnings	$ 339,444	$ 70,894	$ 68,860
Net Actuarial Change in Defined Benefit Plans:
Unrealized Gain During the Period, net of tax expense of $33, $41 and $68	101	131	224
Amortization of Net Actuarial Loss, net of tax (expense) benefit of ($49), $(120), and $149	(154)	(396)	472
Comprehensive Earnings	$ 339,391	$ 70,629	$ 69,556