Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash Flows from Operating Activities:
Net income	$ 62,998	$ 76,785
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	85,082	79,934
Amortization of financing costs	396	250
Amortization of net loss on treasury lock	2,572	(923)
Share-based compensation expense	5,731	4,704
Deferred income tax provision	16,906	14,179
Cellulosic biofuel producer credit reduction	142,251
Alternative fuel mixture credits	(87,897)
Loss on disposals of property, plant and equipment	3,672	5,415
Other, net	6,891	5,401
(Increase) decrease in assets -
Accounts receivable	(26,380)	(34,361)
Inventories	(2,065)	15,535
Prepaid expenses and other current assets	(15,184)	(12,845)
Increase (decrease) in liabilities -
Accounts payable	(23,845)	36,401
Accrued liabilities	(21,083)	(25,292)
Net cash provided by operating activities	150,045	165,183
Cash Flows from Investing Activities:
Additions to property, plant and equipment	(69,322)	(145,150)
Treasury grant proceeds	57,399
Acquisition of businesses	(35,393)	(26,942)
Additions to other long term assets	(1,601)	(6,530)
Proceeds from disposals of property, plant and equipment	20	419
Net cash used for investing activities	(48,897)	(178,203)
Cash Flows from Financing Activities:
Proceeds from long-term debt	397,044
Payments on long-term debt	(7,929)	(330)
Financing costs paid	(892)
Settlement of treasury lock	(65,500)	9,910
Common stock dividends paid	(44,296)	(35,795)
Repurchases of common stock	(33,305)	(45,392)
Proceeds from exercise of stock options	11,184	6,335
Excess tax benefits from share-based awards	1,354	917
Net cash provided by (used for) financing activities	257,660	(64,355)
Net increase (decrease) in cash and cash equivalents	358,808	(77,375)
Cash and cash equivalents, beginning of period	156,313	196,556
Cash and cash equivalents, end of period	$ 515,121	$ 119,181