Annual report pursuant to Section 13 and 15(d)

QUARTERLY RESULTS OF OPERATIONS (Schedule of Quarterly Financial Information) (Details)

v3.19.3.a.u2
QUARTERLY RESULTS OF OPERATIONS (Schedule of Quarterly Financial Information) (Details) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
3 Months Ended 12 Months Ended
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Revenues from product sales and services $ 534.1 $ 555.6 $ 743.2 $ 157.0 $ 696.3 $ 741.8 $ 714.3 $ 180.0 $ 1,989.9 $ 2,332.4 $ 1,866.0
Sales margin 126.9 154.9 263.0 30.9 202.0 261.6 284.5 61.5 575.7 809.6 467.6
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent 63.4 91.8 161.4 (22.1) 624.1 199.8 229.4 (13.4) 294.5 1,039.9 364.5
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent (0.2) (0.9) (0.6) 0.0 (14.6) 238.0 (64.3) (70.9) (1.7) 88.2 2.5
Net Income (Loss) Available to Common Stockholders, Basic $ 63.2 $ 90.9 $ 160.8 $ (22.1) $ 609.5 $ 437.8 $ 165.1 $ (84.3) $ 292.8 $ 1,128.1 $ 367.0
Earnings (loss) per common share attributable to Cliffs common shareholders - basic:                      
Continuing operations $ 0.23 $ 0.34 $ 0.59 $ (0.08) $ 2.11 $ 0.67 $ 0.77 $ (0.05) $ 1.07 $ 3.50 $ 1.27
Discontinued operations 0 0 0 0 (0.05) 0.80 (0.22) (0.24) (0.01) 0.30 0.01
Earnings (loss) per common share attributable to Cliffs common shareholders - basic 0.23 0.34 0.59 (0.08) 2.06 1.47 0.55 (0.29) 1.06 3.80 1.28
Earnings (loss) per common share attributable to Cliffs common shareholders - diluted:                      
Continuing operations 0.23 0.33 0.57 (0.08) 2.03 0.64 0.76 (0.05) 1.04 3.42 1.25
Discontinued operations 0 0 0 0 (0.05) 0.77 (0.21) (0.24) (0.01) 0.29 0.01
Earnings (loss) per common share attributable to Cliffs common shareholders - diluted $ 0.23 $ 0.33 $ 0.57 $ (0.08) $ 1.98 $ 1.41 $ 0.55 $ (0.29) $ 1.03 $ 3.71 $ 1.26
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount                   $ (695.8)  
Share-based Payment Arrangement [Member]                      
Earnings (loss) per common share attributable to Cliffs common shareholders - diluted:                      
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount       4.2       3.8      
Convertible Debt Securities [Member]                      
Earnings (loss) per common share attributable to Cliffs common shareholders - diluted:                      
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount       7.3              
United States [Member]                      
Revenues from product sales and services                 $ 1,505.2 1,847.3 $ 1,504.5
Earnings (loss) per common share attributable to Cliffs common shareholders - diluted:                      
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount                   $ (460.5)