Cleveland-Cliffs Inc. Annual report pursuant to Section 13 and 15(d)

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Schedule of Intangible Asset Lives) (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
All Other Segments [Member] \| Permits [Member] \| Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	15 years
All Other Segments [Member] \| Permits [Member] \| Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	40 years
All Other Segments [Member] \| Utility Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years
All Other Segments [Member] \| Leases [Member] \| Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	4 years 6 months
All Other Segments [Member] \| Leases [Member] \| Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	17 years 6 months
Amapa [Member] \| Investments in Ventures [Member]
Finite-Lived Intangible Assets [Line Items]
Ownership interest, equity method investment		30.00%