Long-Term Debt (Scheduled Remaining Maturity Of Long-Term Debt) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
2013	$ 7,916
2014	17,405
2015	13,173
2016	5,481
2017	6,328
2018 and thereafter	16,362
Derivative, Amount of Hedged Item	956	1,094
Long-term debt	67,621	74,561
Unsecured Debt [Member]
Debt Instrument [Line Items]
2013	807
2014	5,400
2015	5,036
2016	1,907
2017	3,606
2018 and thereafter	15,501
Derivative, Amount of Hedged Item	956	1,094
Long-term debt	33,213	33,650
Unsecured Debt [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
2013	1,008
2014	5,588
2015	5,092
2016	1,970
2017	3,681
2018 and thereafter	16,698
Derivative, Amount of Hedged Item	956
Long-term debt	34,993
Unsecured Debt [Member] | Original Issue Discount [Member]
Debt Instrument [Line Items]
2013	(201)
2014	(188)
2015	(56)
2016	(63)
2017	(75)
2018 and thereafter	(1,197)
Derivative, Amount of Hedged Item	0
Long-term debt	(1,780)
Secured Debt [Member]
Debt Instrument [Line Items]
Derivative, Amount of Hedged Item	0	0
Long-term debt	34,408	40,911
Secured Debt [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
2013	7,109
2014	12,005
2015	8,137
2016	3,574
2017	2,722
2018 and thereafter	861
Derivative, Amount of Hedged Item	0
Long-term debt	$ 34,408