Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net Earnings	$ 54,882	$ 45,344
Adjustments to Reconcile Net Earnings to Net Cash Provided by Operating Activities -
Depreciation, Depletion and Amortization	28,947	22,863
Deferred Income Tax Provision	(3,812)	1,822
Stock Compensation Expense	3,399	2,594
Excess Tax Benefits from Share Based Payment Arrangements		(3,299)
Equity in Earnings of Unconsolidated Joint Venture	(9,876)	(7,980)
Distributions from Joint Venture	4,750	8,750
Changes in Operating Assets and Liabilities:
Accounts and Notes Receivable	(38,527)	(22,057)
Inventories	7,960	2,596
Accounts Payable and Accrued Liabilities	(16,062)	(12,913)
Other Assets	(3,720)	(2,478)
Income Taxes Payable	25,729	18,841
Net Cash Provided by Operating Activities	53,670	54,083
CASH FLOWS FROM INVESTING ACTIVITIES
Property, Plant and Equipment Additions	(16,160)	(8,978)
Net Cash Used in Investing Activities	(16,160)	(8,978)
CASH FLOWS FROM FINANCING ACTIVITIES
Increase (Decrease) in Credit Facility	(25,000)	(9,000)
Dividends Paid to Stockholders	(4,853)	(4,828)
Shares Redeemed to Settle Employee Taxes on Stock Compensation	(1,378)	(2,284)
Purchase and Retirement of Common Stock	(1,880)	(39,135)
Proceeds from Stock Option Exercises	1,273	10,632
Excess Tax Benefits from Share Based Payment Arrangements		3,299
Net Cash Used in Financing Activities	(31,838)	(41,316)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	5,672	3,789
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	6,561	5,391
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 12,233	$ 9,180