Quarterly report pursuant to Section 13 or 15(d)

EARNINGS PER SHARE (Earnings Per Share Computation) (Details)

v3.7.0.1
EARNINGS PER SHARE (Earnings Per Share Computation) (Details) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Income (Loss) from Continuing Operations $ (30.3) $ 114.3
Loss (Income) from Continuing Operations Attributable to Noncontrolling Interest 1.7 (8.8)
Net Income (Loss) from Continuing Operations Attributable to Cliffs Shareholders (28.6) 105.5
Income from Discontinued Operations, net of tax 0.5 2.5
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS $ (28.1) $ 108.0
Weighted Average Number of Shares:    
Basic 265.2 171.7
Employee Stock Plans 0.0 0.3
Diluted 265.2 172.0
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Basic:    
Continuing operations (in dollars per share) $ (0.11) $ 0.61
Discontinued operations (in dollars per share) 0.00 0.01
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Basic (in dollars per share) (0.11) 0.62
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Diluted:    
Continuing operations (in dollars per share) (0.11) 0.61
Discontinued operations (in dollars per share) 0.00 0.01
Earnings (Loss) per Common Share Attributable to Cliffs Common Shareholders - Diluted (in dollars per share) $ (0.11) $ 0.62