Variable Interest Entities - Variable Interests Held by Us and Our Maximum Exposure to Loss Rising From Our Involvements in Those VIEs (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Variable Interest Entity [Line Items]
Variable Interests Held Classified as Assets	$ 1,650	$ 1,392
Variable Interests Held Classified as Liabilities	171	88
Total Assets in Unconsolidated VIEs	21,114	21,594
Maximum Exposure to Loss	3,573	2,470
Asset-backed commercial paper conduits [Member]
Variable Interest Entity [Line Items]
Total Assets in Unconsolidated VIEs	14,261	14,989
Maximum Exposure to Loss	1,550	677
Structured note vehicles [Member]
Variable Interest Entity [Line Items]
Variable Interests Held Classified as Assets	1,650	1,392
Variable Interests Held Classified as Liabilities	171	88
Total Assets in Unconsolidated VIEs	6,853	6,605
Maximum Exposure to Loss	$ 2,023	$ 1,793