Debt (Debt) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Long-term Debt	$ 11,475	$ 11,112
Debt, Current	189	204
Long-term Debt, Excluding Current Maturities	11,286	10,908
Corporate Debt Securities [Member]
Debt Instrument [Line Items]
Long-term Debt	4,989	4,989
Loans Payable [Member]
Debt Instrument [Line Items]
Long-term Debt	2,821	2,828
Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term Debt	1,865	1,901
Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt	1,607	1,191
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 193	$ 203