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

CAPITAL STOCK (Details)

CAPITAL STOCK (Details) $ / shares in Units, $ in Millions	2 Months Ended	3 Months Ended								12 Months Ended
CAPITAL STOCK (Details) $ / shares in Units, $ in Millions	Feb. 21, 2013 $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2014 USD ($) $ / shares shares	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Feb. 11, 2013	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($)	Jan. 04, 2016 shares	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	Mar. 01, 2013 $ / shares
Class of Stock [Line Items]
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
Net proceeds from issuance of Series A, Mandatory Convertible Preferred Stock, Class A \| $										$ 0.0	$ 0.0	$ 709.4
Dividends, Preferred Stock \| $										$ 38.4	$ 51.2	48.7
Common shares, issued (in shares)		159,546,224			159,546,224					159,546,224	159,546,224
Net proceeds from issuance of common shares \| $										$ 0.0	$ 0.0	285.3
Elimination of Dividend \| $ / shares																		$ 0.15
Over Allotment Option [Member]
Class of Stock [Line Items]
Common shares, issued (in shares)	1,350,000
Preferred Class A [Member]
Class of Stock [Line Items]
Series A Mandatory Convertible Preferred Stock, Class A, Percentage										7.00%
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	$ 12.8	$ 12.8	$ 12.8		$ 38.4	$ 51.2	$ 48.7
Issuance of common shares, public offering (in shares)	731,250
Closing price per share (in usd per share) \| $ / shares	$ 25
Common Stock [Member]
Class of Stock [Line Items]
Dividends payable, per share \| $ / shares																			$ 0.150		$ 0.150		$ 0.150	$ 0.15	$ 0.15
Percentage increase (decrease) in dividends payable									76.00%
Issuance of common shares, public offering (in shares)	10,350,000
Common shares, issued (in shares)	9,000,000
Closing price per share (in usd per share) \| $ / shares	$ 29.00
Common Stock [Member] \| Minimum [Member]
Class of Stock [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion		28.1480								28.1480
Convertible Preferred Stock, Shares Issued Upon Conversion per Depositary Share		0.7037								0.7037
Common Stock [Member] \| Maximum [Member]
Class of Stock [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion		34.4840								34.4840
Depositary Shares [Member]
Class of Stock [Line Items]
Depositary Share Offering included in Depositary Share Issuance	27,000,000
Number of Shares included in Depositary Share Issuance due to Exercise of	2,250,000
Preferred Stock, Liquidation Preference Per Share \| $ / shares		$ 25								$ 25
Dividends payable, per share \| $ / shares														$ 0.44	$ 17.5000	$ 0.44	$ 17.5000			$ 0.44		$ 17.5000
Issuance of common shares, public offering (in shares)	29,250,000
Conversion of Preferred Stock [Member] \| Common Stock [Member]
Class of Stock [Line Items]
Convertible Preferred Stock, Common Shares Issued Upon Conversion in Lieu of Dividend													1,300,000
Convertible Preferred Stock, Shares Issued upon Conversion													0.9052
Common shares, issued (in shares)													26,500,000
Convertible Preferred Stock, Common Shares Issued Upon Conversion													25,200,000
Conversion of Preferred Stock [Member] \| Common Stock [Member] \| Minimum [Member]
Class of Stock [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion													0.8621