v3.19.2
Debt (Debt) (Details) - USD ($)
$ in Millions
Jun. 30, 2019
Dec. 31, 2018
Debt Instrument [Line Items]    
Debt and Lease Obligation $ 10,724 $ 10,785
Debt, Current 263 637
Long-term Debt, Excluding Current Maturities 10,461 10,148
Unsecured Debt [Member]    
Debt Instrument [Line Items]    
Debt and Lease Obligation 2,990 3,036
Loans Payable [Member]    
Debt Instrument [Line Items]    
Debt and Lease Obligation 2,979 2,976
Corporate Debt Securities [Member]    
Debt Instrument [Line Items]    
Debt and Lease Obligation 2,402 2,400
Notes Payable, Other Payables [Member]    
Debt Instrument [Line Items]    
Debt and Lease Obligation 1,229 1,264
Secured Debt [Member]    
Debt Instrument [Line Items]    
Debt and Lease Obligation 971 974
Capital 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 $ 75 $ 30