BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Schedule Of Subsidiaries) (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent	100.00%
Northshore [Member]
Related Party Transaction [Line Items]
Entity Address, State or Province	Minnesota
United Taconite [Member]
Related Party Transaction [Line Items]
Entity Address, State or Province	Minnesota
Tilden [Member]
Related Party Transaction [Line Items]
Entity Address, State or Province	Michigan
Noncontrolling Interest, Ownership Percentage by Parent		100.00%
Empire [Member]
Related Party Transaction [Line Items]
Entity Address, State or Province	Michigan
Noncontrolling Interest, Ownership Percentage by Parent		100.00%