Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Sale of business [Member]	Common Stock [Member]	Capital in Excess of Par Value [Member]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Losses [Member]	Accumulated Other Comprehensive Losses [Member] Sale of business [Member]
Beginning balance at Mar. 31, 2018	$ 1,417,690			$ 483	$ 122,379	$ 1,298,840		$ (4,012)
Net Earnings	68,860					68,860
Stock Option Exercises and Restricted Share Vesting	2,104			1	2,103
Purchase and Retirement of Common Stock	(271,988)			(33)	(135,243)	(136,712)
Dividends to Stockholders	(18,636)					(18,636)
Stock Compensation Expense	15,108				15,108
Shares Redeemed to Settle Employee Taxes	(4,347)				(4,347)
Unfunded Pension Liability, net of tax	(696)							(696)
Ending Balance at Mar. 31, 2019	1,209,487			451		1,212,352		(3,316)
Net Earnings	70,894					70,894
Stock Option Exercises and Restricted Share Vesting	3,299			1	3,298
Purchase and Retirement of Common Stock	(313,887)			(36)	(8,114)	(305,737)
Dividends to Stockholders	(16,808)					(16,808)
Stock Compensation Expense	19,822				19,822
Shares Redeemed to Settle Employee Taxes	(4,063)				(4,063)
Unfunded Pension Liability, net of tax	265							265
Ending Balance at Mar. 31, 2020	967,843	$ (636)		416	10,943	960,065	$ (636)	(3,581)
Net Earnings	339,444					339,444
Stock Option Exercises and Restricted Share Vesting	40,457			8	40,449
Stock Compensation Expense	15,291				15,291
Shares Redeemed to Settle Employee Taxes	(4,186)				(4,186)
Unfunded Pension Liability, net of tax	113		$ 254					113	$ 254
Ending Balance at Mar. 31, 2021	$ 1,358,990			$ 424	$ 62,497	$ 1,299,509		$ (3,440)