Long-Term Debt (Long-Term Debt Portfolio) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	$ 15,031	$ 12,573
Long-term Debt, Excluding Current Maturities	45,075	60,894
Derivative, Amount of Hedged Item	595	1,094
Long-term Debt	60,701	74,561
Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	4,445	1,070
Long-term Debt, Excluding Current Maturities	24,291	31,486
Derivative, Amount of Hedged Item	595	1,094
Long-term Debt	29,331	33,650
Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	10,586	11,503
Long-term Debt, Excluding Current Maturities	20,784	29,408
Derivative, Amount of Hedged Item	0	0
Long-term Debt	31,370	40,911
Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	$ 2,600	$ 2,600