Consolidated Statements of Stockholders' Equity - 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, 2015	$ 1,010,593	$ 502	$ 272,441	$ 749,717	$ (12,067)
Net Earnings	152,592			152,592
Stock Option Exercises and Restricted Share Vesting	2,866	2	2,864
Tax Benefit-Stock Option Exercise	4,102		4,102
Purchase and Retirement of Common Stock	(123,530)	(19)	(123,511)
Dividends to Stockholders	(19,823)			(19,823)
Stock Compensation Expense	17,346		17,346
Shares Redeemed to Settle Employee Taxes	(4,273)		(4,273)
Unfunded Pension Liability, net of tax	658				658
Ending Balance at Mar. 31, 2016	1,040,531	485	168,969	882,486	(11,409)
Net Earnings	198,219			198,219
Stock Option Exercises and Restricted Share Vesting	22,108	8	22,100
Tax Benefit-Stock Option Exercise	10,349		10,349
Purchase and Retirement of Common Stock	(60,013)	(9)	(60,004)
Dividends to Stockholders	(19,358)			(19,358)
Stock Compensation Expense	12,069	1	12,068
Shares Redeemed to Settle Employee Taxes	(4,468)		(4,468)
Unfunded Pension Liability, net of tax	4,013				4,013
Ending 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)