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	Jun. 30, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Variable Interest Held Classified as Assets	$ 2,962	$ 2,914
Variable Interests Held Classified as Liabilities	52	46
Total Assets in Unconsolidated VIEs	17,200	16,992
Maximum Exposure to Loss	8,975	8,589
Asset-backed commercial paper conduits [Member]
Variable Interest Entity [Line Items]
Variable Interest Held Classified as Assets	57	29
Variable Interests Held Classified as Liabilities	0	0
Total Assets in Unconsolidated VIEs	11,121	10,984
Maximum Exposure to Loss	3,046	2,685
Structured note vehicles [Member]
Variable Interest Entity [Line Items]
Variable Interest Held Classified as Assets	2,855	2,841
Variable Interests Held Classified as Liabilities	8	7
Total Assets in Unconsolidated VIEs	5,887	5,867
Maximum Exposure to Loss	5,879	5,860
Low income housing partnerships [Member]
Variable Interest Entity [Line Items]
Variable Interest Held Classified as Assets	50	44
Variable Interests Held Classified as Liabilities	44	39
Total Assets in Unconsolidated VIEs	192	141
Maximum Exposure to Loss	$ 50	$ 44