Impairment Charges and Mine Closure Costs (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Impaired Long-Lived Assets Held and Used [Line Items]
Inventory Write-down										$ 2,600,000
Impairment of Long-Lived Assets Held-for-use									142,800,000
Severance Costs										12,300,000
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments										(1,800,000)
Restructuring and Related Cost, Incurred Cost												523,500,000
Asset impairment and mine closure costs	0	200,397,000	20,482,000	0	15,743,000	(2,144,000)	525,583,000	0	220,879,000	539,182,000	7,316,000
Assets, Fair Value Disclosure, Nonrecurring	71,300,000								71,300,000
Productive Land [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Long-Lived Assets Held-for-use										403,300,000
Machinery and Equipment [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Long-Lived Assets Held-for-use										95,600,000
Mining Properties and Mineral Rights [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Intangible Assets, Finite-lived										$ 11,500,000