BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Schedule Of Subsidiaries) (Details)	6 Months Ended
	Jun. 30, 2019
Related Party Transaction [Line Items]
Entity Address, State or Province	OH
Northshore
Related Party Transaction [Line Items]
Entity Address, State or Province	MN
United Taconite
Related Party Transaction [Line Items]
Entity Address, State or Province	MN
Tilden
Related Party Transaction [Line Items]
Entity Address, State or Province	MI
Empire
Related Party Transaction [Line Items]
Entity Address, State or Province	MI
Metallics
Related Party Transaction [Line Items]
Entity Address, State or Province	OH