Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Operating activities:
Net income	$ 102,848	$ 89,904
Income (loss) from discontinued operations, net of tax	(136)	5,006
Income from continuing operations	102,984	84,898
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	188,850	169,007
Earnings, net of distributions, from equity method investments	1,491	1,251
Deferred income taxes	19,790	76,987
Unrealized gain on commodity derivatives	(7,215)	(660)
Changes in current assets and liabilities, net of acquisitions:
Receivables	(65,637)	(2,470)
Inventories	(29,923)	(58,367)
Other current assets	(18,044)	(33,556)
Accounts payable	18,940	(7,119)
Other current liabilities	23,071	(45,562)
Other noncurrent changes	(741)	(9,410)
Net cash provided by continuing operations	233,566	174,999
Net cash provided by (used in) discontinued operations	360	(258)
Net cash provided by operating activities	233,926	174,741
Investing activities:
Capital expenditures	(431,439)	(388,449)
Acquisitions, net of cash acquired	0	(65,767)
Net proceeds from sale or disposition of property and other	20,884	29,454
Investments	16	11,172
Net cash used in continuing operations	(410,539)	(413,590)
Net cash provided by discontinued operations	0	0
Net cash used in investing activities	(410,539)	(413,590)
Financing activities:
Issuance of short-term borrowings	29,600	0
Issuance of long-term debt	450,461	299,945
Repayment of long-term debt	(214,473)	(58,605)
Proceeds from issuance of common stock	0	88
Dividends paid	(32,915)	(63,594)
Excess tax benefit on stock-based compensation	0	26
Contribution from noncontrolling interest	10,000	0
Net cash provided by continuing operations	242,673	177,860
Net cash provided by discontinued operations	0	0
Net cash provided by financing activities	242,673	177,860
Effect of exchange rate changes on cash and cash equivalents	(131)	(140)
Increase (decrease) in cash and cash equivalents	65,929	(61,129)
Cash and cash equivalents - beginning of year	49,042	162,772
Cash and cash equivalents - end of period	$ 114,971	$ 101,643