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

SUBSEQUENT EVENTS Narrative (Details) (USD $)	12 Months Ended	11 Months Ended
SUBSEQUENT EVENTS Narrative (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2013	Jan. 26, 2015	Sep. 30, 2014	May 31, 2015	Jan. 22, 2015
Subsequent Event [Line Items]
Debt Instrument, Par Value	$ 4,144,800,000clf_DebtInstrumentParValue		$ 4,814,800,000clf_DebtInstrumentParValue
Estimated Capital Costs to Develop Bloom Lake Phase II	1,200,000,000
Elimination of Dividend [Member]
Subsequent Event [Line Items]
Elimination of Dividend				$ 0.15
Free Cash Flow Due to Quarterly Dividend Elimination				92,000,000
Revolving Credit Facility [Member]
Subsequent Event [Line Items]
Debt Instrument, Par Value	1,125,000,000		1,750,000,000		1,250,000,000
Revolving Credit Facility [Member] \| Revolving Credit Facility [Member]
Subsequent Event [Line Items]
Debt Instrument, Face Amount, Subsequent Event - Revolving Credit Facility Amendment						750,000,000	900,000,000
Permit Costs and Expenses in connection with Canadian Restructuring EBITDA Add back- Subsequent Event - Revolving Credit Facility Amendment		$ 75,000,000
Limit on Dividend per Share - Subsequent Event - Revolving Credit Facility Amendment		$ 0.01