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

Annual report pursuant to Section 13 and 15(d)

PENSIONS AND OTHER POSTRETIREMENT BENEFITS PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Unobservable Inputs, Level 3) (Details)

PENSIONS AND OTHER POSTRETIREMENT BENEFITS PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Unobservable Inputs, Level 3) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 205.8	$ 188.6	$ 200.5
Defined Benefit Plan, Actual Return on Plan Assets Still Held	15.9	41.0
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	1.5	(25.1)
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	6.8	145.0
Defined Benefit Plan, Divestitures, Plan Assets	(7.0)	(172.8)
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	269.3	251.8	237.0
Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	31.2	29.1	29.3
Defined Benefit Plan, Actual Return on Plan Assets Still Held	3.2	(2.1)
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	3.0	5.2
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	1.4	14.7
Defined Benefit Plan, Divestitures, Plan Assets	(5.5)	(18.0)
Private Equity Funds [Member] \| Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	6.2	6.0
Structured Finance [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	65.4	61.0	56.2
Defined Benefit Plan, Actual Return on Plan Assets Still Held	4.4	33.5
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	(28.7)
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	0	27.5
Defined Benefit Plan, Divestitures, Plan Assets	0	(27.5)
Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	50.0	40.9	29.4
Defined Benefit Plan, Actual Return on Plan Assets Still Held	5.2	5.1
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	(0.4)
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	5.4	36.8
Defined Benefit Plan, Divestitures, Plan Assets	(1.5)	(30.0)
Real Estate [Member] \| Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	8.7	13.2
Structured Credit [Member] \| Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	6.1	13.5
Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	59.2	57.6	85.6
Defined Benefit Plan, Actual Return on Plan Assets Still Held	3.1	4.5
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	(1.5)	(1.2)
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	0	66.0
Defined Benefit Plan, Divestitures, Plan Assets	0	(97.3)
Hedge Funds [Member] \| Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	11.5	24.6
Fair Value, Inputs, Level 3 [Member] \| Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	32.5	57.3	57.8
Defined Benefit Plan, Actual Return on Plan Assets Still Held	2.8	7.5
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	1.9	(2.4)
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	0.1	48.0
Defined Benefit Plan, Divestitures, Plan Assets	(29.6)	(53.6)
Fair Value, Inputs, Level 3 [Member] \| Private Equity Funds [Member] \| Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	6.2	6.0	6.2
Defined Benefit Plan, Actual Return on Plan Assets Still Held	1.0	0.2
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0.4	0.4
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	0.1	0.3
Defined Benefit Plan, Divestitures, Plan Assets	(1.3)	(1.1)
Fair Value, Inputs, Level 3 [Member] \| Real Estate [Member] \| Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	8.7	13.2	15.9
Defined Benefit Plan, Actual Return on Plan Assets Still Held	0.9	2.8
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0.5	(0.7)
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	0	14.2
Defined Benefit Plan, Divestitures, Plan Assets	(5.9)	(19.0)
Fair Value, Inputs, Level 3 [Member] \| Structured Credit [Member] \| Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	6.1	13.5	12.5
Defined Benefit Plan, Actual Return on Plan Assets Still Held	0.4	2.4
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0.4	(1.4)
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	0	11.0
Defined Benefit Plan, Divestitures, Plan Assets	(8.2)	(11.0)
Fair Value, Inputs, Level 3 [Member] \| Hedge Funds [Member] \| Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	11.5	24.6	23.2
Defined Benefit Plan, Actual Return on Plan Assets Still Held	0.5	2.1
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0.6	(0.7)
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	0	22.5
Defined Benefit Plan, Divestitures, Plan Assets	$ (14.2)	$ (22.5)