Net Interest Revenue (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Interest revenue
Non-margin loans	$ 169	$ 169	$ 171	$ 338	$ 342
Margin loans	42	42	32	84	59
Securities:
Taxable	484	503	483	987	956
Exempt from federal income taxes	20	15	8	35	13
Total securities	504	518	491	1,022	969
Deposits in banks	93	114	144	207	272
Deposits with the Federal Reserve and other central banks	39	43	27	82	43
Federal funds sold and securities purchased under resale agreements	9	9	5	18	11
Trading assets	19	17	17	36	39
Total interest revenue	875	912	887	1,787	1,735
Interest expense
Deposits	43	43	68	86	116
Federal funds purchased and securities sold under repurchase agreements			1		2
Trading liabilities	6	4	9	10	22
Other borrowed funds	6	5	5	11	12
Customer payables	2	2	1	4	3
Long-term debt	84	93	72	177	151
Total interest expense	141	147	156	288	306
Net interest revenue	$ 734	$ 765	$ 731	$ 1,499	$ 1,429