Acquisitions and Discontinued Operations - Components of Income (Loss) from Discontinued Operations, Net of Taxes (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Noninterest income	$ 429	$ 457	$ 854	$ 899
Noninterest expense	711	693	1,392	1,372
Income taxes	72	54	142	127
Income (loss) from discontinued operations, net of taxes	5	14	8	13
Segment, Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Noninterest income	10	26	23	38
Noninterest expense	29	31	57	72
Income (loss) before income taxes	9	23	16	21
Income taxes	4	9	8	8
Income (loss) from discontinued operations, net of taxes	5	14	8	13
Segment, Discontinued Operations [Member] | Victory Capital Management [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Noninterest income	28	28	57	58
Noninterest expense	22	21	43	45
Income (loss) before income taxes	6	7	14	13
Income taxes	2	3	5	5
Income (loss) from discontinued operations, net of taxes	4	4	9	8
Segment, Discontinued Operations [Member] | Austin Capital Management [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Noninterest expense		1		9
Income (loss) before income taxes		(1)		(9)
Income taxes			2	(3)
Income (loss) from discontinued operations, net of taxes		$ (1)	$ (2)	$ (6)