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Quarterly report pursuant to Section 13 or 15(d)

SHAREHOLDERS' EQUITY (Narrative) (Details)

v3.20.1
SHAREHOLDERS' EQUITY (Narrative) (Details) - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Mar. 13, 2020
Dec. 31, 2019
Apr. 24, 2019
Nov. 26, 2018
Class of Stock [Line Items] Ìý Ìý Ìý Ìý Ìý Ìý
Common shares, par value $ 0.125 Ìý Ìý $ 0.125 Ìý Ìý
Fair value of Cliffs common shares issued for AK Steel outstanding common stock Ìý Ìý $ 617.6 Ìý Ìý Ìý
Stock Repurchase Program, Authorized Amount Ìý Ìý Ìý Ìý $ 100.0 $ 200.0
Stock Repurchased During Period, Shares Ìý 11,500,000 Ìý Ìý Ìý Ìý
Stock Repurchase Program, Remaining Authorized Repurchase Amount Ìý $ 124.3 Ìý Ìý Ìý Ìý
Preferred Class A [Member] Ìý Ìý Ìý Ìý Ìý Ìý
Class of Stock [Line Items] Ìý Ìý Ìý Ìý Ìý Ìý
Preferred stock, shares authorized (in shares) 3,000,000 Ìý Ìý Ìý Ìý Ìý
Preferred Stock, Shares Issued 0 Ìý Ìý Ìý Ìý Ìý
Preferred Stock, Shares Outstanding 0 Ìý Ìý Ìý Ìý Ìý
Preferred Class B [Member] Ìý Ìý Ìý Ìý Ìý Ìý
Class of Stock [Line Items] Ìý Ìý Ìý Ìý Ìý Ìý
Preferred stock, shares authorized (in shares) 4,000,000 Ìý Ìý Ìý Ìý Ìý
Preferred Stock, Shares Issued 0 Ìý Ìý Ìý Ìý Ìý
Preferred Stock, Shares Outstanding 0 Ìý Ìý Ìý Ìý Ìý
Common Stock [Member] Ìý Ìý Ìý Ìý Ìý Ìý
Class of Stock [Line Items] Ìý Ìý Ìý Ìý Ìý Ìý
Stock Issued During Period, Shares, Acquisitions 126,800,000 Ìý Ìý Ìý Ìý Ìý
Fair value of Cliffs common shares issued for AK Steel outstanding common stock Ìý $ 0.0 $ 617.6 Ìý Ìý Ìý
Stock Repurchased During Period, Shares Ìý 11,500,000 Ìý Ìý Ìý Ìý