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

FAIR VALUE OF FINANCIAL INSTRUMENTS (Fair Value Of Assets And Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Assets:
Cash equivalents	$ 177.0	$ 30.0
Derivative Asset	33.1	7.8
Total Asset	210.1	37.8
Liabilities:
Derivative Liability	0.5	4.0
Total Liability	0.5	4.0
Fair Value, Inputs, Level 1 [Member]
Assets:
Cash equivalents	177.0	30.0
Derivative Asset	0.0	0.0
Total Asset	177.0	30.0
Liabilities:
Derivative Liability	0.0	0.0
Total Liability	0.0	0.0
Fair Value, Inputs, Level 2 [Member]
Assets:
Cash equivalents	0.0	0.0
Derivative Asset	1.5	0.0
Total Asset	1.5	0.0
Liabilities:
Derivative Liability	0.0	0.6
Total Liability	0.0	0.6
Fair Value, Inputs, Level 3 [Member]
Assets:
Cash equivalents	0.0	0.0
Derivative Asset	31.6	7.8
Total Asset	31.6	7.8
Liabilities:
Derivative Liability	0.5	3.4
Total Liability	$ 0.5	$ 3.4