Annual report pursuant to Section 13 and 15(d)

Benefit Plans and Collective Bargaining Agreements - United Steelworkers Narrative (Details)

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Benefit Plans and Collective Bargaining Agreements - United Steelworkers Narrative (Details) - USD ($)
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Defined Contribution Plan Disclosure [Line Items]      
Employer contributions to defined benefit plans $ 200,000    
Total employer contributions to plans under collective-bargaining arrangements $ 28,469 $ 32,034 $ 29,042
401(k) Employee Stock Ownership Plan      
Defined Contribution Plan Disclosure [Line Items]      
Employee maximum contribution percentage 100.00%    
Employee maximum contribution amount $ 19,000    
Minimum age to qualify under Economic Growth and Tax Relief Reconciliation Act 50 years    
Employee additional contribution eligible under economic growth and tax relief reconciliation act $ 6,000    
Employee maximum contribution eligible under economic growth and tax relief reconciliation act 25,000    
Employer discretionary contribution 0 0 0
Matching contributions made by employer $ 800,000 700,000 600,000
401(k) and Profit Sharing Plan      
Defined Contribution Plan Disclosure [Line Items]      
Employee maximum contribution percentage 60.00%    
Employee maximum contribution amount $ 19,000    
Minimum age to qualify under Economic Growth and Tax Relief Reconciliation Act 50 years    
Employee additional contribution eligible under economic growth and tax relief reconciliation act $ 6,000    
Employee maximum contribution eligible under economic growth and tax relief reconciliation act $ 25,000    
Employer contribution as a percentage of participant's eligible compensation 3.00%    
Employer contributions to defined benefit plans   200,000 200,000
Employer discretionary contribution $ 0 0 0
Maximum | Other Pension, Postretirement and Supplemental Plans      
Defined Contribution Plan Disclosure [Line Items]      
Employer contributions to defined benefit plans $ 200,000 $ 100,000 $ 100,000
Funding percentage under defined benefit plans   80.00%  
Employer contribution percentage of each participant's eligible compensation 4.25%    
Employer's contribution percentage of total contributions 5.00%