Cleveland-Cliffs Inc. Quarterly report pursuant to Section 13 or 15(d)

SEGMENT REPORTING Segment Reporting (Summary of Assets by Segment) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Assets	$ 2,702.6us-gaap_Assets	$ 3,164.0us-gaap_Assets
U.S. Iron Ore [Member]
Segment Reporting Information [Line Items]
Assets	1,550.1	1,464.9
Asia Pacific Iron Ore [Member]
Segment Reporting Information [Line Items]
Assets	250.6	274.6
All Other Segments [Member]
Segment Reporting Information [Line Items]
Assets	31.2	147.0
Total Segment Assets [Member]
Segment Reporting Information [Line Items]
Assets	1,831.9	1,886.5
Corporate [Member]
Segment Reporting Information [Line Items]
Assets	673.5	546.8
Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Disposal Group, Including Discontinued Operation, Assets	$ 197.2	$ 730.7