Variable Interest Entities and Securitizations - Carrying Amount of Assets and Liabilities of Variable Interest Entities (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Variable Interest Entity [Line Items]
Carrying Amount of Assets, Consolidated	$ 37,373	$ 40,812
Carrying Amount of Liabilities, Consolidated	11,338	12,770
Carrying Amount of Assets, Unconsolidated	3,534	3,264
Carrying Amount of Liabilities, Unconsolidated	476	478
Maximum exposure to loss	4,189	3,767
Affordable housing entities
Variable Interest Entity [Line Items]
Carrying Amount of Assets, Consolidated	0	0
Carrying Amount of Liabilities, Consolidated	0	0
Carrying Amount of Assets, Unconsolidated	3,250	2,969
Carrying Amount of Liabilities, Unconsolidated	443	463
Maximum exposure to loss	3,250	2,969
Entities that provide capital to low-income and rural communities
Variable Interest Entity [Line Items]
Carrying Amount of Assets, Consolidated	391	389
Carrying Amount of Liabilities, Consolidated	99	98
Carrying Amount of Assets, Unconsolidated	1	1
Carrying Amount of Liabilities, Unconsolidated	0	0
Maximum exposure to loss	1	1
Other
Variable Interest Entity [Line Items]
Carrying Amount of Assets, Consolidated	6	1
Carrying Amount of Liabilities, Consolidated	0	1
Carrying Amount of Assets, Unconsolidated	80	95
Carrying Amount of Liabilities, Unconsolidated	0	0
Maximum exposure to loss	80	95
Other VIEs
Variable Interest Entity [Line Items]
Carrying Amount of Assets, Consolidated	397	390
Carrying Amount of Liabilities, Consolidated	99	99
Carrying Amount of Assets, Unconsolidated	3,331	3,065
Carrying Amount of Liabilities, Unconsolidated	443	463
Maximum exposure to loss	3,331	3,065
Credit card loan securitizations
Variable Interest Entity [Line Items]
Carrying Amount of Assets, Consolidated	36,976	40,422
Carrying Amount of Liabilities, Consolidated	11,239	12,671
Carrying Amount of Assets, Unconsolidated	0	0
Carrying Amount of Liabilities, Unconsolidated	0	0
Maximum exposure to loss	0	0
Home loan securitizations
Variable Interest Entity [Line Items]
Carrying Amount of Assets, Consolidated	0	0
Carrying Amount of Liabilities, Consolidated	0	0
Carrying Amount of Assets, Unconsolidated	203	199
Carrying Amount of Liabilities, Unconsolidated	33	15
Maximum exposure to loss	858	702
Securitization-related VIEs
Variable Interest Entity [Line Items]
Carrying Amount of Assets, Consolidated	36,976	40,422
Carrying Amount of Liabilities, Consolidated	11,239	12,671
Carrying Amount of Assets, Unconsolidated	203	199
Carrying Amount of Liabilities, Unconsolidated	33	15
Maximum exposure to loss	$ 858	$ 702