Credit Loss Reserves - Analysis of Credit Loss Reserves (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit loss reserve balances at beginning of period	$ 4,608	$ 4,590	$ 5,952	$ 5,512
Provision for credit losses	287	2,182	1,816	3,473
Charge-offs	(488)	(973)	(2,266)	(3,468)
Recoveries	22	112	225	394
Total net charge-offs	(466)	(861)	(2,041)	(3,074)
Reserves on receivables transferred to held for sale	(1,298)		(1,298)
Credit loss reserve balance at end of period	$ 4,429	$ 5,911	$ 4,429	$ 5,911