Long-Term Debt (Long-Term Debt Portfolio) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	$ 15,997	$ 17,172
Long-term Debt, Excluding Current Maturities	51,839	51,848
Derivative, Amount of Hedged Item	459	445
Long-term Debt	68,295	69,465
Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	4,365	5,321
Long-term Debt, Excluding Current Maturities	19,108	21,425
Derivative, Amount of Hedged Item	459	445
Long-term Debt	23,932	27,191
Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	11,632	11,851
Long-term Debt, Excluding Current Maturities	32,731	30,423
Derivative, Amount of Hedged Item	0	0
Long-term Debt	44,363	42,274
Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	$ 2,600	$ 2,600