CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
ASSETS
Cash and cash equivalents	$ 128,680	$ 128,430
Receivables, net	194,217	313,343
Inventories	316,505	240,437
Deferred income taxes	56,645	61,079
Prepaid expenses	63,733	49,974
Other current assets	36,928	45,649
Total current assets	796,708	838,912
Mineral interests, net of accumulated depletion of $132.3 million and $84.2 million, respectively	3,010,448	3,056,258
Property, plant and equipment, net of accumulated depreciation of $687.1 million and $614.6 million, respectively	1,739,506	1,631,333
Deferred income taxes	106,848	109,300
Goodwill	1,066,754	1,066,754
Other long-term assets	134,891	153,951
Total assets	6,855,155	6,856,508
LIABILITIES AND STOCKHOLDERS' EQUITY
Current debt	49,890	56,695
Accounts payable	155,524	112,661
Accrued expenses	233,749	229,067
Accumulated postretirement benefits obligation	28,181	27,247
Other current liabilities	45,885	63,757
Total current liabilities	513,229	489,427
Long-term debt	2,206,866	2,269,020
Deferred income taxes	1,007,065	1,029,336
Accumulated postretirement benefits obligation	556,758	550,671
Other long-term liabilities	370,908	381,537
Total liabilities	4,654,826	4,719,991
Commitments and contingencies (Note 10)
Stockholders' equity:
Common stock, $0.01 par value per share: Authorized-200,000,000 shares, Issued-62,511,717 and 62,444,905 shares, respectively	625	624
Capital in excess of par value	1,624,652	1,620,430
Retained earnings	801,162	744,939
Accumulated other comprehensive income (loss):
Pension and other postretirement benefit plans, net of tax	(217,746)	(225,541)
Foreign currency translation adjustment	(4,066)	(3,276)
Unrealized loss on hedges, net of tax	(4,057)	(787)
Unrealized investment gain (loss), net of tax	(241)	128
Total stockholders' equity	2,200,329	2,136,517
Total liabilities and stockholders' equity	$ 6,855,155	$ 6,856,508