Annual report pursuant to Section 13 and 15(d)

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

v3.8.0.1
Income Taxes - Net Operating Loss and Tax Credit Carryforwards (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Tax Credit Carryforward [Line Items]    
Deferred Tax Asset $ 1,793 $ 3,125
Operating Loss Carryforwards [Line Items]    
Deferred Tax Asset 8,506 $ 9,199
Net operating losses before benefit of federal deductions 2,100  
Valuation allowance before considering benefit of federal deductions 739  
General business credits    
Tax Credit Carryforward [Line Items]    
Deferred Tax Asset 1,721  
Valuation Allowance 0  
Net Deferred Tax Asset 1,721  
Foreign tax credits    
Tax Credit Carryforward [Line Items]    
Deferred Tax Asset 72  
Valuation Allowance (72)  
Net Deferred Tax Asset 0  
Net operating losses - U.S.    
Operating Loss Carryforwards [Line Items]    
Deferred Tax Asset 868  
Valuation Allowance 0  
Net Deferred Tax Asset 868  
Net operating losses – U.K. and Other non-U.S.    
Operating Loss Carryforwards [Line Items]    
Deferred Tax Asset 657  
Valuation Allowance (578)  
Net Deferred Tax Asset 79  
Net operating losses – U.K. and Other non-U.S. | United Kingdom    
Operating Loss Carryforwards [Line Items]    
Deferred Tax Asset 5,347  
Valuation Allowance 0  
Net Deferred Tax Asset 5,347  
Net operating losses – U.S. states    
Operating Loss Carryforwards [Line Items]    
Deferred Tax Asset 1,634  
Valuation Allowance (584)  
Net Deferred Tax Asset $ 1,050