Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2022
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income (Loss)	$ 477,639	$ 461,540	$ 374,247
Adjustments to Reconcile Net Earnings to Net Cash Provided by Operating Activities, Net of Effect of Noncash Activity:
Depreciation, Depletion, and Amortization	149,832	138,554	128,811
Write-off of debt issuance costs	0	0	6,101
Deferred Income Tax Provision	7,953	4,475	6,383
Stock Compensation Expense	19,900	17,155	14,264
Equity in Earnings of Unconsolidated Joint Venture	(31,581)	(35,474)	(32,488)
Distributions from Joint Venture	7,000	27,000	27,250
Changes in Operating Assets and Liabilities:
Accounts and Notes Receivable	(551)	(12,035)	(29,209)
Inventories	(67,232)	(47,946)	(912)
Accounts Payable and Accrued Liabilities	13,794	(7,797)	27,192
Other Assets	(20,468)	4,955	(1,331)
Income Taxes Receivable	7,652	(8,701)	(3,137)
Net Cash Provided by Operating Activities	563,938	541,726	517,171
CASH FLOWS FROM INVESTING ACTIVITIES
Additions to Property, Plant, and Equipment	(120,305)	(110,143)	(74,121)
Acquisition Spending	(55,053)	(158,451)	0
Proceeds from Sale of Businesses	0	0	0
Net Cash Provided by (Used in) Investing Activities	(175,358)	(268,594)	(74,121)
CASH FLOWS FROM FINANCING ACTIVITIES
Borrowings Under Revolving Credit Facility	13,000	200,000	200,000
Repayment of Borrowings Under Revolving Credit Facility	0	(43,000)	0
Proceeds from 2.500% Senior Unsecured Notes	0	0	743,692
Repayment of 4.500% Senior Unsecured Notes	0	0	(350,000)
Repayment of Term Loan	(10,000)	(7,500)	(665,000)
Dividends Paid to Stockholders	(35,298)	(37,496)	(30,770)
Purchase and Retirement of Common Stock	(343,274)	(387,717)	(589,742)
Proceeds from Stock Option Exercises	17,098	5,418	21,366
Premium Paid on Early Retirement of Senior Notes	0	0	(8,407)
Payment of Debt Issuance Costs	0	(903)	(7,985)
Shares Redeemed to Settle Employee Taxes on Stock Compensation	(10,423)	(6,108)	(5,308)
Net Cash Used in Financing Activities	(368,897)	(277,306)	(692,154)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	19,683	(4,174)	(249,104)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	15,242	19,416	268,520
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 34,925	$ 15,242	$ 19,416