Income Taxes - Effective tax rates (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Income tax reconciliation
Tax expense (benefit) at the U.S. federal statutory income tax rate									$ (93)		$ (318)		$ 239
State and local taxes, net of federal benefit									22		46		92
Adjustment of tax rate used to value deferred taxes									0		(13)		0
Non-deductible expense accrual related to certain regulatory matters									0	[1]	483	[1]	0	[1]
Non-deductible goodwill related to branch sale									0	[1]	139	[1]	0	[1]
Non-deductible goodwill impairment charges									215	[2]	0	[2]	0	[2]
Valuation allowance									0	[3]	0	[3]	(217)	[3]
Other non-deductible / non-taxable items									(11)	[4]	(14)	[4]	3	[4]
Items affecting prior periods									(13)	[5]	0	[5]	1	[5]
Uncertain tax positions									20	[6]	45	[6]	161	[6]
Impact of foreign operations									13	[7]	51	[7]	63	[7]
Low income housing tax credits									(84)		(85)		(115)
Other									2		4		0
Total income tax expense	$ (93)	$ 11	$ 49	$ 104	$ (19)	$ (12)	$ 351	$ 18	$ 71		$ 338		$ 227
Effective income tax reconciliation
Tax expense (benefit) at the U.S. federal statutory income tax rate, percentage									(35.00%)		(35.00%)		35.00%
State and local taxes, net of federal benefit, percentage									8.20%		5.10%		13.50%
Adjustment of tax rate used to value deferred taxes, percentage									0.00%		(1.40%)		0.00%
Non-deductible expense accrual related to certain regulatory matters, percentage									0.00%	[1]	53.10%	[1]	0.00%	[1]
Non-deductible goodwill related to branch sale, percentage									0.00%	[1]	15.30%	[1]	0.00%	[1]
Non-deductible goodwill impairment charges, percentage									80.50%	[2]	0.00%	[2]	0.00%	[2]
Valuation allowance, percentage									0.00%	[3]	0.00%	[3]	(31.80%)	[3]
Other non-deductible / non-taxable items, percentage									(4.10%)	[4]	(1.50%)	[4]	0.40%	[4]
Items affecting prior periods, percentage									(4.90%)	[5]	0.00%	[5]	0.10%	[5]
Uncertain tax positions, percentage									7.50%	[6]	4.90%	[6]	23.60%	[6]
Impact of foreign operations, percentage									4.90%	[7]	5.60%	[7]	9.20%	[7]
Low income housing tax credits, percentage									(31.20%)		(9.40%)		(16.70%)
Other, percentage									0.70%		0.40%		0.00%
Effective tax rate, percentage									26.60%		37.10%		33.30%

[1] Represents non-deductible expense relating to certain regulatory matters and non-deductible goodwill related to the branches sold to First Niagara in 2012.

[2] Represents non-deductible goodwill impairment related to our Global Banking and Markets reporting unit in the fourth quarter of 2013.

[3] For 2011, relates to release of valuation allowance previously established on foreign tax credits.

[4] For 2013 and 2012, mainly relates to tax exempt interest income. For 2011, relates to tax exempt income and tax credits.

[5] For 2013 and 2011, relates to corrections to current and deferred tax balance sheet accounts and changes in estimates as a result of filing the federal and state income tax returns.

[6] Reflects changes in state uncertain tax positions which no longer meet the more likely than not requirement for recognition. Specifically, the increase in 2011 relates to a state court decision that required us to increase our reserves.

[7] For 2013 and 2012, relates to foreign (U.K.) tax expense for which no foreign tax credits are allowed, and for 2011, primarily relates to the reversal of an accrued foreign tax expense related to Brazilian withholding taxes.