v3.19.3
Debt (Debt) (Details) - USD ($)
$ in Millions
Sep. 30, 2019
Dec. 31, 2018
Debt Instrument [Line Items]    
Debt and Lease Obligation $ 10,642 $ 10,785
Debt, Current 229 637
Long-term Debt, Excluding Current Maturities 10,413 10,148
Unsecured Debt [Member]    
Debt Instrument [Line Items]    
Debt and Lease Obligation 2,991 3,036
Loans Payable [Member]    
Debt Instrument [Line Items]    
Debt and Lease Obligation 3,175 2,976
Corporate Debt Securities [Member]    
Debt Instrument [Line Items]    
Debt and Lease Obligation 2,404 2,400
Notes Payable, Other Payables [Member]    
Debt Instrument [Line Items]    
Debt and Lease Obligation 965 1,264
Secured Debt [Member]    
Debt Instrument [Line Items]    
Debt and Lease Obligation 969 974
Finance Lease Obligations [Member]    
Debt Instrument [Line Items]    
Debt and Lease Obligation 78 105
Revolving Credit Facility [Member]    
Debt Instrument [Line Items]    
Debt and Lease Obligation $ 60 $ 30