v3.19.1
Debt (Debt) (Details) - USD ($)
$ in Millions
Mar. 31, 2019
Dec. 31, 2018
Debt Instrument [Line Items]    
Debt and Capital Lease Obligations $ 10,791 $ 10,785
Debt, Current 258 637
Long-term Debt, Excluding Current Maturities 10,533 10,148
Unsecured Debt [Member]    
Debt Instrument [Line Items]    
Debt and Capital Lease Obligations 2,989 3,036
Loans Payable [Member]    
Debt Instrument [Line Items]    
Debt and Capital Lease Obligations 2,972 2,976
Corporate Debt Securities [Member]    
Debt Instrument [Line Items]    
Debt and Capital Lease Obligations 2,401 2,400
Notes Payable, Other Payables [Member]    
Debt Instrument [Line Items]    
Debt and Capital Lease Obligations 1,228 1,264
Secured Debt [Member]    
Debt Instrument [Line Items]    
Debt and Capital Lease Obligations 972 974
Capital Lease Obligations [Member]    
Debt Instrument [Line Items]    
Debt and Capital Lease Obligations 79 105
Revolving Credit Facility [Member]    
Debt Instrument [Line Items]    
Debt and Capital Lease Obligations $ 150 $ 30