Consolidated Statements of Comprehensive Earnings (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net Earnings	$ 71,793	$ 72,603	$ 113,097	$ 138,942
Net Actuarial Change in Defined Benefit Plans:
Amortization of net actuarial loss	43	73	88	146
Tax expense	(10)	(17)	(20)	(34)
Comprehensive Earnings	$ 71,826	$ 72,659	$ 113,165	$ 139,054