Consolidated Statements of Stockholders' Equity (unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Capital in Excess of Par Value [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Losses [Member]
Beginning balance at Mar. 31, 2017	$ 1,203,450	$ 485	$ 149,014	$ 1,061,347	$ (7,396)
Net Earnings	256,632			256,632
Stock Option Exercises and Restricted Share Vesting	24,264	3	24,261
Purchase and Retirement of Common Stock	(61,078)	(5)	(61,073)
Dividends to Stockholders	(19,404)			(19,404)
Stock Compensation Expense	14,079		14,079
Cumulative Impact of the Adoption of ASU 2016-09			713	(713)
Reclassification of Income Tax Effects to Retained Earnings				978	(978)
Shares Redeemed to Settle Employee Taxes	(4,974)		(4,974)
Other	359		359
Unfunded Pension Liability, net of tax	4,362				4,362
Ending Balance at Mar. 31, 2018	1,417,690	483	122,379	1,298,840	(4,012)
Net Earnings	138,942			138,942
Stock Option Exercises and Restricted Share Vesting	1,992		1,992
Purchase and Retirement of Common Stock	(122,404)	(12)	(122,392)
Dividends to Stockholders	(9,503)			(9,503)
Stock Compensation Expense	7,559	1	7,558
Shares Redeemed to Settle Employee Taxes	(1,785)		(1,785)
Unfunded Pension Liability, net of tax	112				112
Ending Balance at Sep. 30, 2018	$ 1,432,603	$ 472	$ 7,752	$ 1,428,279	$ (3,900)