Long-Term Debt (Long-Term Debt Portfolio) (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	$ 12,005	$ 17,438
Long-term Debt, Excluding Current Maturities	53,523	48,668
Derivative, Amount of Hedged Item	324	452
Long-term debt	65,852	66,558
Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	465	4,809
Long-term Debt, Excluding Current Maturities	18,778	17,154
Derivative, Amount of Hedged Item	324	452
Long-term debt	19,567	22,415
Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	11,540	12,629
Long-term Debt, Excluding Current Maturities	34,745	31,514
Derivative, Amount of Hedged Item	0	0
Long-term debt	46,285	44,143
Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	$ 2,600	$ 2,600