Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash Flows from Operating Activities:
Consolidated net earnings	$ 184,548	$ 167,169
Adjustments to reconcile consolidated net earnings to net cash provided by operating activities:
Depreciation, depletion and amortization	146,102	139,617
Stock-based compensation expense	17,727	12,801
Gain on divestitures and sales of assets	(17,514)	(261)
Deferred income taxes	2,464	34,389
Other items, net	(4,393)	(5,767)
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Accounts receivable, net	(112,708)	(117,524)
Inventories, net	(28,240)	(33,131)
Accounts payable	11,663	32,521
Other assets and liabilities, net	29,950	(19,970)
Net Cash Provided by Operating Activities	229,599	209,844
Cash Flows from Investing Activities:
Additions to property, plant and equipment	(216,089)	(210,559)
Acquisitions, net	(2,200)	(123,000)
Cash received in acquisition		3,446
Proceeds from divestitures and sales of assets	32,089	4,474
Payment of railcar construction advances	(40,930)
Reimbursement of railcar construction advances	40,930
Net Cash Used for Investing Activities	(186,200)	(325,639)
Cash Flows from Financing Activities:
Borrowings of debt	941,244	280,000
Repayments of debt	(845,023)	(70,420)
Payments on capital lease obligations	(1,752)	(1,563)
Debt issuance costs	(1,055)
Change in bank overdraft	3,795	(3,092)
Contributions by owners of noncontrolling interest	211
Dividends paid	(53,135)	(51,467)
Proceeds from exercise of stock options	7,937	18,070
Shares withheld for employees' income tax obligations	(8,938)	(5,546)
Repurchases of common stock	(99,999)	(190,000)
Net Cash Used for Financing Activities	(56,715)	(24,018)
Net Decrease in Cash and Cash Equivalents	(13,316)	(139,813)
Cash and Cash Equivalents, beginning of period	50,038	168,409
Cash and Cash Equivalents, end of period	$ 36,722	$ 28,596