Annual report pursuant to Section 13 and 15(d)

STOCK COMPENSATION PLANS - Performance Shares (Details)

v3.20.4
STOCK COMPENSATION PLANS - Performance Shares (Details) - $ / shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Performance Shares [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]        
Outstanding at beginning of year 1,935,878 1,424,723 1,848,312  
Outstanding shares, weighted average grant date fair value $ 10.34 $ 15.58 $ 14.46 $ 13.42
Granted shares 2,510,853 572,104 675,599  
Granted Shares Weighted Average Fair Value $ 5.49 $ 18.31 $ 11.93  
Distributed (1,938,786) 0 (489,953)  
Distributed shares, weighted average grant date fair value $ 12.23 $ 0 $ 10.89  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Performance Conditions Adjustment in Period 549,154 0 (560,720)  
Performance adjustment, weighted average grant date fair value $ 15.63 $ 0 $ 10.69  
Forfeited/canceled shares (604,873) (60,949) (48,515)  
Forfeited/canceled shares, weighted average grant date fair value $ 5.70 $ 15.12 $ 19.33  
Outstanding at end of year 2,452,226 1,935,878 1,424,723  
Performance/vesting period 3 years      
Performance Shares [Member] | Minimum [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]        
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage 0.00%      
Performance Shares [Member] | Maximum [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]        
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage 200.00%      
Performance Shares [Member] | AK Steel [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]        
Granted shares 500,000      
Distributed shares, weighted average grant date fair value $ 4.59      
Outstanding at end of year 100,000      
Long-term Performance Plan | AK Steel [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]        
Granted shares 1,000,000.0      
Outstanding at end of year 300,000