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Impairments Long-lived Assets (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]      
Goodwill $ 20,851   $ 21,451
Property, plant and equipment, net 36,041   $ 36,419
CO2      
Finite-Lived Intangible Assets [Line Items]      
Asset impairment charges 950    
Oil and Gas Properties | CO2      
Finite-Lived Intangible Assets [Line Items]      
Asset impairment charges $ 350 $ 0  
Valuation Technique, Discounted Cash Flow [Member] | CO2      
Finite-Lived Intangible Assets [Line Items]      
Estimated Weighted Average Cost Of Capital 9.25%    
Valuation Technique, Discounted Cash Flow [Member] | Oil and Gas Properties | CO2      
Finite-Lived Intangible Assets [Line Items]      
Estimated Weighted Average Cost Of Capital 10.50%