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 (Narrative) (Details)

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Current Fiscal Year End Date	--12-31
Minimum participants percentage	15.00%
Accumulated benefit obligation for defined benefit pension plans	$ 1,204,400,000	$ 1,091,400,000
Maturity period of security	10 years
Reserve for investment commitments	55,500,000clf_ReserveForInvestmentCommitments			45,000,000clf_ReserveForInvestmentCommitments
Sei Special Situations Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Redemption request notice period, days	95 days
Structured Finance [Member]
Defined Benefit Plan Disclosure [Line Items]
Redemption request notice period, days	90 days
Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Redemption request notice period, days	45 days
Withdrawal request notice period, days	65 days
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase in Projected Benefit Obligation due to new mortality tables	30,000,000
Percentage Increase in Projected Benefit Obligation due to new mortality tables	4.00%
Defined Benefit Plan, Net Periodic Benefit Cost	31,300,000	52,100,000	55,200,000
Annual costs for defined contribution plan	6,300,000	6,800,000	6,700,000
Participant contributions	0	0
Other Postretirement Benefit Expense	(700,000)	17,400,000	28,100,000
Pension and Other Postretirement Benefit Expense	36,900,000	76,300,000	90,000,000
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	(10,900,000)	0
Increase in Canadian Plan Projected Benefit Obligation due to new mortality tables	12,000,000
Percentage Increase in Canadian Plan Projected Benefit Obligation due to new mortality tables	5.00%
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	(2,900,000)	0	0
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase in Projected Benefit Obligation due to new mortality tables	20,000,000
Percentage Increase in Projected Benefit Obligation due to new mortality tables	7.00%
Defined Benefit Plan, Net Periodic Benefit Cost	(700,000)	17,400,000	28,100,000
Participant contributions	4,800,000	5,600,000
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	(8,800,000)	0
Increase in Canadian Plan Projected Benefit Obligation due to new mortality tables	3,000,000
Percentage Increase in Canadian Plan Projected Benefit Obligation due to new mortality tables	5.00%
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	7,900,000	0	0
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.72%
Expected period of long-term return on assets	3 years
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.92%
Expected period of long-term return on assets	5 years
United States [Member] \| Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.83%	4.57%
Projected yield, number of bonds used	715
United States [Member] \| Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.83%	4.57%
Canada [Member] \| Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.75%	4.50%
Projected yield, number of bonds used	285
Canada [Member] \| Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.75%	4.75%
Tilden, Empire, Hibbing and United Taconite [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of USW employees covered by labor contracts	2,200
Percentage of total workforce covered by labor contract	40.90%
Pinnacle Complex and Oak Grove [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of USW employees covered by labor contracts	800
Percentage of total workforce covered by labor contract	15.20%
Contribution rate per hour worked	8.16	8.10	8.10
Annual costs for defined contribution plan	14,900,000	13,800,000
Underfunded Liability Estimate	330,000,000
Prior To Age65 [Member] \| Defined Benefit Postretirement Health Coverage [Member] \| United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Annual limit on medical coverage for each participant	7,000
Prior To Age65 [Member] \| Minimum [Member] \| Defined Benefit Postretirement Health Coverage [Member] \| Northshore [Member]
Defined Benefit Plan Disclosure [Line Items]
Annual limit on medical coverage for each participant	4,020
Prior To Age65 [Member] \| Maximum [Member] \| Defined Benefit Postretirement Health Coverage [Member] \| Northshore [Member]
Defined Benefit Plan Disclosure [Line Items]
Annual limit on medical coverage for each participant	4,500
After Age65 [Member] \| Defined Benefit Postretirement Health Coverage [Member] \| United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Annual limit on medical coverage for each participant	3,000
After Age65 [Member] \| Defined Benefit Postretirement Health Coverage [Member] \| Northshore [Member]
Defined Benefit Plan Disclosure [Line Items]
Annual limit on medical coverage for each participant	$ 2,000