Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
CASH FLOWS FROM OPERATING ACTIVITIES
Net Earnings	$ 70,004	$ 31,931
Adjustments to Reconcile Net Earnings to Net Cash Provided by Operating Activities -
Depreciation, Depletion and Amortization	34,624	25,444
Deferred Income Tax Provision	(3,594)	(6,683)
Stock Compensation Expense	4,816	4,139
Excess Tax Benefits from Share Based Payment Arrangements	(1,053)	(149)
Equity in Earnings of Unconsolidated Joint Venture	(17,625)	(15,218)
Distributions from Joint Venture	20,500	14,250
Changes in Operating Assets and Liabilities:
Accounts and Notes Receivable	(30,132)	(17,749)
Inventories	(7,712)	14,602
Accounts Payable and Accrued Liabilities	(2,894)	5,766
Other Assets	(1,203)	(2,095)
Income Taxes Payable	13,524	12,522
Net Cash Provided by Operating Activities	79,255	66,760
CASH FLOWS FROM INVESTING ACTIVITIES
Property, Plant and Equipment Additions	(31,583)	(8,628)
Net Cash Used in Investing Activities	(31,583)	(8,628)
CASH FLOWS FROM FINANCING ACTIVITIES
Decrease in Credit Facility	(34,000)	(50,000)
Dividends Paid to Stockholders	(9,910)	(9,057)
Proceeds from Stock Option Exercises	2,351	3,365
Shares Redeemed to Settle Employee Taxes on Stock Compensation	(435)	(921)
Excess Tax Benefits from Share Based Payment Arrangements	1,053	149
Net Cash Used in Financing Activities	(40,941)	(56,464)
NET INCREASE IN CASH AND CASH EQUIVALENTS	6,731	1,668
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	3,897	6,481
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 10,628	$ 8,149