CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
ASSETS
Cash and cash equivalents	$ 404,715	$ 260,818
Receivables, net	254,874	281,763
Inventories	311,167	312,647
Deferred income taxes	33,864	37,067
Prepaid expenses	29,261	39,022
Other current assets	14,209	18,031
Total current assets	1,048,090	949,348
Mineral interests, net	2,887,136	2,905,002
Property, plant and equipment, net	1,615,419	1,637,552
Other long-term assets	98,020	98,958
Total assets	5,648,665	5,590,860
LIABILITIES AND STOCKHOLDERS' EQUITY
Current debt	15,379	9,210
Accounts payable	72,213	92,712
Accrued expenses	165,633	133,870
Accumulated other postretirement benefits obligation	30,462	30,036
Other current liabilities	225,851	214,073
Total current liabilities	509,538	479,901
Long-term debt	2,918,066	2,769,622
Accumulated other postretirement benefits obligation	573,324	570,712
Deferred income taxes	790,263	822,867
Other long-term liabilities	187,865	195,064
Total liabilities	4,979,056	4,838,166
Stockholders' equity:
Common stock, $0.01 par value per share: Authorized-200,000,000 shares; issued- 62,623,268 and 62,577,924 shares, respectively	626	626
Capital in excess of par value	1,614,987	1,613,256
Accumulated deficit	(791,108)	(698,930)
Accumulated other comprehensive loss	(154,896)	(162,258)
Total stockholders' equity	669,609	752,694
Total liabilities and stockholders' equity	$ 5,648,665	$ 5,590,860