LINES OF CREDIT AND LONG-TERM DEBT - Additional Information (Detail) (USD $) In Millions, unless otherwise specified		0 Months Ended	3 Months Ended		0 Months Ended
	Mar. 31, 2014 10.75% Senior Notes	Feb. 07, 2014 Senior Notes Due 2018	Mar. 31, 2014 Senior Notes Due 2018	Mar. 31, 2014 Term Debt [Member]	Dec. 24, 2013 Sherritt International Corporation [Member]	Mar. 31, 2014 Subsequent Event Add-On Notes	Mar. 31, 2014 Kemmerer Mine
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 425.0				$ 425.0
Debt Instrument Price As Percentage Of Face Value		106.875%
Proceeds from Issuance of Debt		454.2
Debt Instrument, Unamortized Premium		29.2
Stated interest rate (percent)	10.75%	10.75%	10.75%	8.02%		10.75%
Debt issuance costs capitalized			7.6
Payments to Acquire Businesses, Gross					293
Cash Bonding Obligations Financed By Net Proceeds Of Debt Issued		58
Payments for Debt Issuance and Business Acquisition Transaction Costs		26
Debt Instrument, Redemption Price, Percentage			101.00%
Capital Lease Obligations							$ 12.9