Annual report pursuant to Section 13 and 15(d)

ACQUISITIONS - Intangible assets and liabilities (Details)

v3.20.4
ACQUISITIONS - Intangible assets and liabilities (Details) - AK Steel [Member]
$ in Millions
 12 Months Ended
Dec. 31, 2020
USD ($)
Acquired Finite-Lived Intangible Assets [Line Items]  
Finite-lived Intangible Assets Acquired $ 148.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life 17 years
Finite-lived Intangible Liability Assumed $ (71.0)
Assumed Finite-lived Intangible Liabilities, Weighted Average Useful Life 12 years
Customer Relationships  
Acquired Finite-Lived Intangible Assets [Line Items]  
Finite-lived Intangible Assets Acquired $ 77.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life 18 years
Technology-Based Intangible Assets  
Acquired Finite-Lived Intangible Assets [Line Items]  
Finite-lived Intangible Assets Acquired $ 60.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life 17 years
Trademarks and Trade Names  
Acquired Finite-Lived Intangible Assets [Line Items]  
Finite-lived Intangible Assets Acquired $ 11.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life 10 years