Consolidated Statements of Cash Flows (unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
CASH FLOWS FROM OPERATING ACTIVITIES
Net Earnings	$ 88,029	$ 70,004
Adjustments to Reconcile Net Earnings to Net Cash Provided by Operating Activities -
Depreciation, Depletion and Amortization	34,864	34,624
Deferred Income Tax Provision	(3,628)	(3,594)
Stock Compensation Expense	6,702	4,816
Excess Tax Benefits from Share Based Payment Arrangements	(3,195)	(1,053)
Equity in Earnings of Unconsolidated Joint Venture	(21,851)	(17,625)
Distributions from Joint Venture	19,375	20,500
Changes in Operating Assets and Liabilities:
Accounts and Notes Receivable	(29,809)	(30,132)
Inventories	(3,615)	(7,712)
Accounts Payable and Accrued Liabilities	16,878	(2,894)
Other Assets	2,798	(1,203)
Income Taxes Payable	11,103	13,524
Net Cash Provided by Operating Activities	117,651	79,255
CASH FLOWS FROM INVESTING ACTIVITIES
Property, Plant and Equipment Additions	(40,039)	(31,583)
Net Cash Used in Investing Activities	(40,039)	(31,583)
CASH FLOWS FROM FINANCING ACTIVITIES
Decrease in Credit Facility	(69,000)	(34,000)
Dividends Paid to Stockholders	(10,019)	(9,910)
Proceeds from Stock Option Exercises	4,092	2,351
Shares Redeemed to Settle Employee Taxes on Stock Compensation	(1,299)	(435)
Excess Tax Benefits from Share Based Payment Arrangements	3,195	1,053
Net Cash Used in Financing Activities	(73,031)	(40,941)
NET INCREASE IN CASH AND CASH EQUIVALENTS	4,581	6,731
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	6,482	3,897
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 11,063	$ 10,628