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

Annual report pursuant to Section 13 and 15(d)

CAPITAL STOCK (Details)

CAPITAL STOCK (Details) $ / shares in Units, $ in Millions	3 Months Ended							9 Months Ended	12 Months Ended
CAPITAL STOCK (Details) $ / shares in Units, $ in Millions	Dec. 31, 2016 USD ($) $ / shares shares	Sep. 30, 2016 USD ($)	Dec. 31, 2015 USD ($) $ / shares shares	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Feb. 11, 2013	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($)	Aug. 10, 2016 $ / shares	Mar. 31, 2016 USD ($)	Nov. 02, 2015 $ / shares	Aug. 03, 2015 $ / shares	May 01, 2015 $ / shares	Feb. 02, 2015 $ / shares	Jan. 26, 2015 $ / shares	Dec. 03, 2014 $ / shares	Nov. 03, 2014 $ / shares	Sep. 02, 2014 $ / shares	Aug. 01, 2014 $ / shares	Jun. 03, 2014 $ / shares	Mar. 03, 2014 $ / shares
Class of Stock [Line Items]
Gain on extinguishment/restructuring of debt									$ 166.3	$ 392.9	$ 16.2
Common Stock, New Shares, Issued \| shares									44,400,000
Depositary Share Interest in a Share of 7% Series A Mandatory Convertible Preferred Stock, Class A									0.025
Common Stock, Par or Stated Value Per Share \| $ / shares	$ 0.125		$ 0.125						$ 0.125	$ 0.125
Trading Day Window Determining Number of Common Shares Issuable on Conversion									20
Dividends, Preferred Stock									$ 0.0	$ 38.4	51.2
Common shares, issued (in shares) \| shares	238,636,794		159,546,224						238,636,794	159,546,224
Net proceeds from issuance of common shares								$ 287.6	$ 287.4	$ 0.0	0.0
Elimination of Dividend \| $ / shares																		$ 0.15
Current Fiscal Year End Date									--12-31
Common Shares Issued in Debt to Equity Exchange \| shares	8,200,000								8,200,000
Debt Instrument, Face Amount Exchanged						$ 674.6							$ 512.2
Shares Issued, Price Per Share \| $ / shares												$ 6.75
Preferred Class A [Member]
Class of Stock [Line Items]
Preferred Stock, Liquidation Preference Per Share \| $ / shares	$ 1,000		$ 1,000						$ 1,000	$ 1,000
Dividends payable, per share \| $ / shares														$ 17.5000	$ 0.44	$ 17.50	$ 0.44			$ 17.5000		$ 0.44
Dividends, Preferred Stock			$ 0.0	$ 25.6	$ 0.0	12.8			$ 0.0	$ 38.4	$ 51.2
Common Stock [Member]
Class of Stock [Line Items]
Convertible Preferred Stock, Common Shares Issued Upon Conversion in Lieu of Dividend \| shares	1,300,000								1,300,000
Convertible Preferred Stock, Shares Issued upon Conversion \| shares	0.7037								0.7037
Convertible Preferred Stock, Shares Issued Upon Conversion per Depositary Share \| shares	0.9052								0.9052
Dividends payable, per share \| $ / shares																			$ 0.150		$ 0.150		$ 0.150	$ 0.150
Increase Decrease In Dividends Payable Percentage							76.00%
Common shares, issued (in shares) \| shares	26,500,000.0000								26,500,000.0000
Convertible Preferred Stock, Common Shares Issued Upon Conversion \| shares	25,200,000.0000								25,200,000.0000
Common Stock [Member] \| Minimum [Member]
Class of Stock [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion \| shares	28.1480								28.1480
Convertible Preferred Stock, Shares Issued Upon Conversion per Depositary Share \| shares	0.8621								0.8621
Common Stock [Member] \| Maximum [Member]
Class of Stock [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion \| shares	34.4840								34.4840
Depositary Shares [Member]
Class of Stock [Line Items]
Dividends payable, per share \| $ / shares														$ 0.44	$ 17.5000	$ 0.44	$ 17.5000			$ 0.44		$ 17.5000
Exchange of Debt for Equity [Member]
Class of Stock [Line Items]
Gain on extinguishment/restructuring of debt	$ 11.3
$500 Million 3.95% 2018 Senior Notes [Member]
Class of Stock [Line Items]
Gain on extinguishment/restructuring of debt		$ (19.9)
Debt Instrument, Face Amount Exchanged													17.6
$500 Million 3.95% 2018 Senior Notes [Member] \| Exchange of Debt for Equity [Member]
Class of Stock [Line Items]
Debt Instrument, Face Amount Exchanged	10.0								$ 10.0
$218.5 Million 8.00% 2020 1.5 Lien Notes [Member]
Class of Stock [Line Items]
Debt Instrument, Face Amount Received in Debt Exchange of $500M 3.95% Notes													11.4
Debt Instrument, Face Amount Received in Debt Exchange of $500M 4.80% Notes													17.9
Debt instrument, Face Amount Received in Debt Exchange of $700M 4.875% Notes													30.5
$218.5 Million 8.00% 2020 1.5 Lien Notes [Member] \| Exchange of Debt for Equity [Member]
Class of Stock [Line Items]
Debt Instrument, Face Amount Exchanged	20.1								20.1
$700 Million 4.875% 2021 Senior Notes[Member]
Class of Stock [Line Items]
Debt Instrument, Face Amount Exchanged						$ 208.5							$ 76.3
$700 Million 4.875% 2021 Senior Notes[Member] \| Exchange of Debt for Equity [Member]
Class of Stock [Line Items]
Debt Instrument, Face Amount Exchanged	$ 26.8								$ 26.8