Annual report pursuant to Section 13 and 15(d)

STOCK COMPENSATION PLANS - Nonemployee Directors (Details)

v3.20.4
STOCK COMPENSATION PLANS - Nonemployee Directors (Details) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount $ 14,000,000    
Restricted Stock Units (RSUs) [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted shares 1,160,928 572,104 685,599
Restricted Stock Units (RSUs) [Member] | AK Steel [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted shares 300,000    
Share-based Payment Arrangement, Nonemployee [Member] | Director [Member] | Directors Plan [Member] | Restricted Stock Units (RSUs) [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted shares 253,809 86,477 92,718
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount $ 100,000    
Share-based Payment Arrangement, Nonemployee [Member] | Director [Member] | Deferred Compensation, Share-based Payments [Member] | Directors Plan [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted shares 54,794 23,659 17,170