Long-Term Debt (Long-Term Debt Portfolio) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	$ 15,373	$ 12,573
Long-term Debt, Excluding Current Maturities	48,469	60,894
Derivative, Amount of Hedged Item	692	1,094
Long-term Debt	64,534	74,561
Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	4,494	1,070
Long-term Debt, Excluding Current Maturities	27,749	31,486
Derivative, Amount of Hedged Item	692	1,094
Long-term Debt	32,935	33,650
Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	10,879	11,503
Long-term Debt, Excluding Current Maturities	20,720	29,408
Derivative, Amount of Hedged Item	0	0
Long-term Debt	31,599	40,911
Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	$ 2,600	$ 2,600