Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES
Net Earnings	$ 186,853us-gaap_NetIncomeLoss	$ 124,243us-gaap_NetIncomeLoss	$ 57,744us-gaap_NetIncomeLoss
Adjustments to Reconcile Net Earnings to Net Cash Provided by Operating Activities, Net of Effect of Non-Cash Activity -
Depreciation, Depletion and Amortization	76,299	70,021	56,850
Deferred Income Tax Provision	5,805us-gaap_DeferredIncomeTaxExpenseBenefit	5,746us-gaap_DeferredIncomeTaxExpenseBenefit	6,155us-gaap_DeferredIncomeTaxExpenseBenefit
Stock Compensation Expense	13,030us-gaap_ShareBasedCompensation	10,136us-gaap_ShareBasedCompensation	9,002us-gaap_ShareBasedCompensation
Excess Tax Benefits from Share Based Payment Arrangements	(5,743)	(8,067)	(6,493)
Equity in Earnings of Unconsolidated Joint Venture	(44,967)	(37,811)	(32,507)
Distributions from Joint Venture	40,375	37,750	28,500
Changes in Operating Assets and Liabilities:
Accounts and Notes Receivable	4,196	(12,876)	(7,771)
Inventories	(38,741)us-gaap_IncreaseDecreaseInInventories	(32,714)us-gaap_IncreaseDecreaseInInventories	(14,186)us-gaap_IncreaseDecreaseInInventories
Accounts Payable and Accrued Liabilities	(11,499)	6,504	24,610
Other Assets	520	(3,511)	(2,679)
Income Taxes Payable	7,993	11,212	5,182
Net Cash Provided by Operating Activities	234,121	170,633	124,407
CASH FLOWS FROM INVESTING ACTIVITIES
Additions to Property, Plant and Equipment	(111,573)	(59,490)	(53,011)
CRS Acquisition	(237,171)		(453,420)
Net Cash Used in Investing Activities	(348,744)	(59,490)	(506,431)
CASH FLOWS FROM FINANCING ACTIVITIES
Increase (Decrease) in Credit Facility	141,000	(108,000)	227,000
Repayment of Senior Notes	(9,500)us-gaap_RepaymentsOfSeniorDebt		(4,677)us-gaap_RepaymentsOfSeniorDebt
Dividends Paid to Stockholders	(20,072)us-gaap_PaymentsOfDividendsCommonStock	(19,899)us-gaap_PaymentsOfDividendsCommonStock	(18,533)us-gaap_PaymentsOfDividendsCommonStock
Net Proceeds from Offering of Common Stock			154,832
Proceeds from Stock Option Exercises	4,311	14,187	19,645
Shares Redeemed to Settle Employee Taxes on Stock Compensation	(4,166)	(2,913)	(3,569)
Payment of Debt Issuance Costs	(1,661)us-gaap_PaymentsOfDebtIssuanceCosts		(1,751)us-gaap_PaymentsOfDebtIssuanceCosts
Excess Tax Benefits from Share Based Payment Arrangements	5,743	8,067	6,493
Net Cash Provided by (Used in) Financing Activities	115,655	(108,558)	379,440
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	1,032	2,585	(2,584)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	6,482	3,897	6,481
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 7,514	$ 6,482	$ 3,897

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.