Variable Interest Entities - Variable Interests Held by Us and Our Maximum Exposure to Loss Rising From Our Involvements in Those VIEs (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Variable Interest Entity [Line Items]
Variable Interests Held Classified as Assets	$ 1,827	$ 2,117
Variable Interests Held Classified as Liabilities	117	154
Total Assets in Unconsolidated VIEs	22,928	23,159
Maximum Exposure to Loss	4,381	4,429
Asset-backed commercial paper conduits [Member]
Variable Interest Entity [Line Items]
Variable Interests Held Classified as Assets	0	0
Variable Interests Held Classified as Liabilities	0	0
Total Assets in Unconsolidated VIEs	16,273	16,104
Maximum Exposure to Loss		2,212
Structured note vehicles [Member]
Variable Interest Entity [Line Items]
Variable Interests Held Classified as Assets	1,827	2,117
Variable Interests Held Classified as Liabilities	117	154
Total Assets in Unconsolidated VIEs	6,655	7,055
Maximum Exposure to Loss	$ 1,927	$ 2,217