Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash Flows from Operating Activities:
Consolidated net earnings	$ 42,307	$ 45,055
Adjustments to reconcile consolidated net earnings to net cash provided by operating activities:
Depreciation, depletion and amortization	70,376	68,410
Stock-based compensation expense	10,275	7,228
Loss (Gain) on divestitures and sales of assets	73	(100)
Deferred income taxes	2,827	17,988
Other items, net	2	(2,036)
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Accounts receivable, net	(21,305)	(29,695)
Inventories, net	(15,375)	(13,495)
Accounts payable	8,536	9,231
Other assets and liabilities, net	(23,670)	(34,274)
Net Cash Provided by Operating Activities	74,046	68,312
Cash Flows from Investing Activities:
Additions to property, plant and equipment	(102,095)	(94,228)
Acquisitions, net		(123,000)
Cash received in acquisition		3,446
Proceeds from divestitures and sales of assets	539	3,415
Payment of railcar construction advances	(37,011)
Reimbursement of railcar construction advances	37,011
Net Cash Used for Investing Activities	(101,556)	(210,367)
Cash Flows from Financing Activities:
Borrowings of debt	205,000	210,000
Repayments of debt	(45,012)	(26,390)
Payments on capital lease obligations	(761)	(780)
Change in bank overdraft		(10,235)
Dividends paid	(26,560)	(25,847)
Issuances of common stock	3,917	4,720
Shares withheld for employees' income tax obligations	(3,695)	(580)
Repurchases of common stock	(99,999)	(150,000)
Net Cash Provided by Financing Activities	32,890	888
Net Increase (Decrease) in Cash and Cash Equivalents	5,380	(141,167)
Cash and Cash Equivalents, beginning of period	50,038	168,409
Cash and Cash Equivalents, end of period	$ 55,418	$ 27,242