Basis of Presentation and Significant Accounting Policies (Significant Consolidated Subsidiaries) (Details)	6 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Dec. 31, 2002
Northshore [Member]
Location	Minnesota
Ownership Interest	100.00%
Operation	Iron Ore
United Taconite [Member]
Location	Minnesota
Ownership Interest	100.00%
Operation	Iron Ore
Wabush [Member]
Location	Labrador/Quebec, Canada
Ownership Interest	100.00%
Operation	Iron Ore
Bloom Lake [Member]
Location	Quebec, Canada
Ownership Interest	75.00%
Operation	Iron Ore
Tilden [Member]
Location	Michigan
Ownership Interest	85.00%
Operation	Iron Ore
Empire [Member]
Location	Michigan
Ownership Interest	79.00%	79.00%	46.70%
Operation	Iron Ore
Asia Pacific Iron Ore [Member]
Location	Western Australia
Ownership Interest	100.00%
Operation	Iron Ore
Pinnacle [Member]
Location	West Virginia
Ownership Interest	100.00%
Operation	Coal
Oak Grove [Member]
Location	Alabama
Ownership Interest	100.00%
Operation	Coal
CLCC [Member]
Location	West Virginia
Ownership Interest	100.00%
Operation	Coal
renewaFUEL [Member]
Location	Michigan
Ownership Interest	95.00%
Operation	Biomass
Freewest [Member]
Location	Ontario, Canada
Ownership Interest	100.00%
Operation	Chromite
Spider [Member]
Location	Ontario, Canada
Ownership Interest	100.00%
Operation	Chromite