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Long-Term Debt - CEI Senior Secured Notes due 2025 (Details) - USD ($)
$ in Millions
Dec. 31, 2021
Jul. 06, 2020
Long-term debt    
Interest rate (as a percent) 4.30%  
CEI Senior Secured Notes | Senior Notes    
Long-term debt    
Interest rate (as a percent) 6.25%  
CEI Senior Secured Notes | Senior Notes | Estimate of Fair Value Measurement    
Long-term debt    
Long-term debt, gross $ 3,400 $ 3,400