v3.7.0.1
Debt (Debt) (Details) - USD ($)
$ in Millions
Jun. 30, 2017
Dec. 31, 2016
Debt Instrument [Line Items]    
Debt and Capital Lease Obligations $ 11,922 $ 12,179
Debt, Current 615 748
Long-term Debt, Excluding Current Maturities 11,307 11,431
Unsecured Debt [Member]    
Debt Instrument [Line Items]    
Debt and Capital Lease Obligations 3,414 3,412
Loans Payable [Member]    
Debt Instrument [Line Items]    
Debt and Capital Lease Obligations 3,403 3,165
Corporate Debt Securities [Member]    
Debt Instrument [Line Items]    
Debt and Capital Lease Obligations 1,842 2,290
Notes Payable, Other Payables [Member]    
Debt Instrument [Line Items]    
Debt and Capital Lease Obligations 1,595 1,597
Secured Debt [Member]    
Debt Instrument [Line Items]    
Debt and Capital Lease Obligations 1,547 1,553
Capital Lease Obligations [Member]    
Debt Instrument [Line Items]    
Debt and Capital Lease Obligations $ 121 $ 162