Annual report pursuant to Section 13 and 15(d)

STOCK COMPENSATION PLANS - Stock Options (Details)

v3.20.4
STOCK COMPENSATION PLANS - Stock Options (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]        
Outstanding at beginning of year 563,230 563,230 599,870  
Granted shares 2,010,277 0 0  
Granted shares, weighted average exercise price $ 11.86 $ 0 $ 0  
Exercised, number of shares (79,973) 0 (36,640)  
Exercised, weighted average exercise price $ 7.01 $ 0 $ 7.70  
Forfeited/canceled, shares (7,726) 0 0  
Forfeitured/canceled, weighted average exercise price $ 41.04 $ 0 $ 0  
Outstanding at end of year 2,485,808 563,230 563,230  
Outstanding, weighted average exercise price $ 11.60 $ 10.42 $ 10.42 $ 10.25
Exercisable, shares 2,172,052 563,230 563,230  
Exercisable, weighted average exercise price $ 11.86 $ 10.42 $ 10.42  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term 3 years 2 months 12 days      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value $ 11      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term 2 years 6 months      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value $ 9      
AK Steel [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]        
Granted shares 2,000,000.0      
Granted shares, weighted average exercise price $ 0.51