Income Taxes - Effective tax rates (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Income Tax [Line Items]
Tax expense (benefit) at the U.S. federal statutory income tax rate	$ (278)	$ 101	$ (328)	$ 235
State and local taxes, net of federal benefit	14	5	23	42
Change in tax rate used to value deferred taxes			(10)
Valuation allowance on deferred tax assets		8		(135)
Non-deductible expense accrual related to certain regulatory matters	280		525
Non-deductible goodwill related to sale of branches	33		139
Validation of current liability accounts	(34)		22
Tax exempt interest income	(6)	(3)	(11)	(8)
Low income housing and other tax credits	(21)	(21)	(63)	(63)
Foreign tax credits and other credits	(8)	(8)	(23)	(20)
Impact of foreign operations	8	31	23	43
Uncertain tax provision	(9)	6	57	151
Other	8	(2)	3	(7)
Effective tax rate	$ (12)	$ 117	$ 357	$ 238
Tax expense (benefit) at the U.S. federal statutory income tax rate	(35.00%)	35.00%	(35.00%)	35.00%
State and local taxes, net of federal benefit	1.80%	1.80%	2.50%	6.00%
Change in tax rate used to value deferred taxes, percentage			(1.10%)
Valuation allowance on deferred tax assets, percentage		2.70%		(19.30%)
Non-deductible expense accrual related to certain regulatory matters	35.30%		56.00%
Non-deductible goodwill related to sale of branches	4.20%		14.80%
Validation of current liability accounts	(4.30%)		2.30%
Tax exempt interest income	(0.80%)	(1.00%)	(1.20%)	(1.10%)
Low income housing and other tax credits	(2.60%)	(7.00%)	(6.70%)	(9.00%)
Foreign tax credits and other credits	(1.00%)	(3.40%)	(2.50%)	(3.00%)
Impact of foreign operations	1.00%	11.20%	2.50%	6.30%
Uncertain tax provision reserves	(1.10%)	1.90%	6.10%	21.50%
Other	1.00%	(0.70%)	0.40%	(0.90%)
Effective tax rate	(1.50%)	40.50%	38.10%	35.50%