Annual report pursuant to Section 13 and 15(d)

Income Taxes - Net Operating Loss and Tax Credit Carryforwards (Details)

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Income Taxes - Net Operating Loss and Tax Credit Carryforwards (Details) - USD ($)
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Operating Loss Carryforwards [Line Items]    
Deferred Tax Asset $ 7,417,000,000 $ 7,993,000,000
Tax Credit Carryforward [Line Items]    
Deferred Tax Asset 183,000,000 $ 623,000,000
Net operating losses before benefit of federal deductions 1,700,000,000  
Valuation allowance before considering benefit of federal deductions 734,000,000  
Foreign tax credits    
Tax Credit Carryforward [Line Items]    
Deferred Tax Asset 183,000,000  
Valuation Allowance (183,000,000)  
Net Deferred Tax Asset 0  
Net operating losses - U.S.    
Operating Loss Carryforwards [Line Items]    
Deferred Tax Asset 312,000,000  
Valuation Allowance 0  
Net Deferred Tax Asset 312,000,000  
Net operating losses – non-U.S.    
Operating Loss Carryforwards [Line Items]    
Deferred Tax Asset 493,000,000  
Valuation Allowance (423,000,000)  
Net Deferred Tax Asset 70,000,000  
Net operating losses – non-U.S. | United Kingdom    
Operating Loss Carryforwards [Line Items]    
Deferred Tax Asset 5,276,000,000  
Valuation Allowance 0  
Net Deferred Tax Asset 5,276,000,000  
Net operating losses – U.S. states    
Operating Loss Carryforwards [Line Items]    
Deferred Tax Asset 1,336,000,000  
Valuation Allowance (580,000,000)  
Net Deferred Tax Asset $ 756,000,000