SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Variable Interest Entities) (Details) (Absaloka Mine, Variable Interest Entity, Primary Beneficiary [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013
Variable Interest Entity [Line Items]
Variable Interest Entity, Ownership Percentage	50.00%
Decrease to other liabilities due to cessation of operations	$ 19.1
Decrease to noncontrolling interest due to cessation of operations	$ 18.1
Subsequent Event
Variable Interest Entity [Line Items]
Variable Interest Entity, Ownership Percentage	100.00%

Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 5A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=28200181&loc=SL6759159-111685

Name:	us-gaap_VariableInterestEntityOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration