Fair Value Measurement and Fair Value of Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Fair value measurements
Trading account assets	$ 941	$ 851
Securities available for sale	14,663
Residential mortgage-backed securities, U.S. government agency and government-sponsored agencies
Fair value measurements
Securities available for sale	8,157
Residential mortgage-backed securities, Privately issued
Fair value measurements
Securities available for sale	191
Collateralized loan obligations
Fair value measurements
Securities available for sale	2,534
Asset-backed and other
Fair value measurements
Securities available for sale	19
Other debt securities, Direct bank purchase bonds
Fair value measurements
Securities available for sale	1,897
Other debt securities, Other
Fair value measurements
Securities available for sale	52
Level 3
Fair value measurements
Other assets	4	3
Fair Value Measurements Recurring
Fair value measurements
Trading account assets	941	851
Securities available for sale	14,670	15,817
Other assets	42	10
Total assets	15,653	16,678
Percentage of Total	100.00%	100.00%
Percentage of Total Company Assets	14.00%	16.00%
Trading account liabilities	664	540
FDIC clawback liability	102	96
Other liabilities	109	113
Total liabilities	773	653
Percentage of Total	100.00%	100.00%
Percentage of Total Company Liabilities	1.00%	1.00%
Fair Value Measurements Recurring | U.S. Treasury
Fair value measurements
Trading account assets	25	8
Fair Value Measurements Recurring | U.S. government-sponsored agencies
Fair value measurements
Trading account assets	121	116
Securities available for sale		73
Fair Value Measurements Recurring | State and municipal
Fair value measurements
Trading account assets	24	5
Fair Value Measurements Recurring | Other loans
Fair value measurements
Trading account assets		140
Fair Value Measurements Recurring | Interest rate derivative contracts
Fair value measurements
Trading account assets	647	501
Trading account liabilities	263	230
Fair Value Measurements Recurring | Commodity derivative contracts
Fair value measurements
Trading account assets	69	10
Trading account liabilities	28	28
Fair Value Measurements Recurring | Foreign exchange derivative contracts
Fair value measurements
Trading account assets	15	15
Trading account liabilities	32	18
Fair Value Measurements Recurring | Equity Derivative contracts
Fair value measurements
Trading account assets	40	56
Trading account liabilities	287	254
Fair Value Measurements Recurring | Residential mortgage-backed securities, U.S. government agency and government-sponsored agencies
Fair value measurements
Securities available for sale	8,157	8,900
Fair Value Measurements Recurring | Residential mortgage-backed securities, Privately issued
Fair value measurements
Securities available for sale	191	222
Fair Value Measurements Recurring | Privately issued commercial mortgage-backed securities
Fair value measurements
Securities available for sale	1,813	1,870
Fair Value Measurements Recurring | Collateralized loan obligations
Fair value measurements
Securities available for sale	2,534	2,673
Fair Value Measurements Recurring | Asset-backed and other
Fair value measurements
Securities available for sale	19	35
Fair Value Measurements Recurring | Other debt securities, Direct bank purchase bonds
Fair value measurements
Securities available for sale	1,897	1,960
Fair Value Measurements Recurring | Other debt securities, Other
Fair value measurements
Securities available for sale	52	76
Fair Value Measurements Recurring | Equity securities
Fair value measurements
Securities available for sale	7	8
Fair Value Measurements Recurring | Interest rate hedging contracts
Fair value measurements
Other assets	40	8
Other liabilities	2	13
Fair Value Measurements Recurring | Other derivative contracts
Fair value measurements
Other assets	2	2
Other liabilities	5	4
Fair Value Measurements Recurring | Securities sold, not yet purchased
Fair value measurements
Trading account liabilities	54	10
Fair Value Measurements Recurring | Level 1
Fair value measurements
Trading account assets	1	2
Securities available for sale	7	8
Total assets	8	10
Trading account liabilities	4	4
Total liabilities	4	4
Percentage of Total	1.00%	1.00%
Fair Value Measurements Recurring | Level 1 | Interest rate derivative contracts
Fair value measurements
Trading account assets	1	1
Trading account liabilities	4	3
Fair Value Measurements Recurring | Level 1 | Foreign exchange derivative contracts
Fair value measurements
Trading account assets		1
Trading account liabilities		1
Fair Value Measurements Recurring | Level 1 | Equity securities
Fair value measurements
Securities available for sale	7	8
Fair Value Measurements Recurring | Level 2
Fair value measurements
Trading account assets	1,091	1,071
Securities available for sale	12,718	13,791
Other assets	40	9
Total assets	13,849	14,871
Percentage of Total	89.00%	89.00%
Percentage of Total Company Assets	12.00%	14.00%
Trading account liabilities	872	695
Other liabilities	4	14
Total liabilities	876	709
Percentage of Total	113.00%	109.00%
Percentage of Total Company Liabilities	1.00%	1.00%
Fair Value Measurements Recurring | Level 2 | U.S. Treasury
Fair value measurements
Trading account assets	25	8
Fair Value Measurements Recurring | Level 2 | U.S. government-sponsored agencies
Fair value measurements
Trading account assets	121	116
Securities available for sale		73
Fair Value Measurements Recurring | Level 2 | State and municipal
Fair value measurements
Trading account assets	24	5
Fair Value Measurements Recurring | Level 2 | Other loans
Fair value measurements
Trading account assets		140
Fair Value Measurements Recurring | Level 2 | Interest rate derivative contracts
Fair value measurements
Trading account assets	790	705
Trading account liabilities	667	606
Fair Value Measurements Recurring | Level 2 | Commodity derivative contracts
Fair value measurements
Trading account assets	108	67
Trading account liabilities	98	53
Fair Value Measurements Recurring | Level 2 | Foreign exchange derivative contracts
Fair value measurements
Trading account assets	23	30
Trading account liabilities	53	26
Fair Value Measurements Recurring | Level 2 | Residential mortgage-backed securities, U.S. government agency and government-sponsored agencies
Fair value measurements
Securities available for sale	8,157	8,900
Fair Value Measurements Recurring | Level 2 | Residential mortgage-backed securities, Privately issued
Fair value measurements
Securities available for sale	191	222
Fair Value Measurements Recurring | Level 2 | Privately issued commercial mortgage-backed securities
Fair value measurements
Securities available for sale	1,813	1,870
Fair Value Measurements Recurring | Level 2 | Collateralized loan obligations
Fair value measurements
Securities available for sale	2,534	2,673
Fair Value Measurements Recurring | Level 2 | Asset-backed and other
Fair value measurements
Securities available for sale	19	35
Fair Value Measurements Recurring | Level 2 | Other debt securities, Other
Fair value measurements
Securities available for sale	4	18
Fair Value Measurements Recurring | Level 2 | Interest rate hedging contracts
Fair value measurements
Other assets	40	8
Other liabilities	2	13
Fair Value Measurements Recurring | Level 2 | Other derivative contracts
Fair value measurements
Other assets		1
Other liabilities	2	1
Fair Value Measurements Recurring | Level 2 | Securities sold, not yet purchased
Fair value measurements
Trading account liabilities	54	10
Fair Value Measurements Recurring | Level 3
Fair value measurements
Trading account assets	303	271
Securities available for sale	1,945	2,018
Other assets	2	1
Total assets	2,250	2,290
Percentage of Total	14.00%	14.00%
Percentage of Total Company Assets	2.00%	2.00%
Trading account liabilities	298	264
FDIC clawback liability	102	96
Other liabilities	105	99
Total liabilities	403	363
Percentage of Total	52.00%	55.00%
Fair Value Measurements Recurring | Level 3 | Interest rate derivative contracts
Fair value measurements
Trading account assets	6	7
Fair Value Measurements Recurring | Level 3 | Commodity derivative contracts
Fair value measurements
Trading account assets	9	9
Trading account liabilities	9	8
Fair Value Measurements Recurring | Level 3 | Foreign exchange derivative contracts
Fair value measurements
Trading account assets	2	2
Trading account liabilities	2	2
Fair Value Measurements Recurring | Level 3 | Equity Derivative contracts
Fair value measurements
Trading account assets	286	253
Trading account liabilities	287	254
Fair Value Measurements Recurring | Level 3 | Other debt securities, Direct bank purchase bonds
Fair value measurements
Securities available for sale	1,897	1,960
Fair Value Measurements Recurring | Level 3 | Other debt securities, Other
Fair value measurements
Securities available for sale	48	58
Fair Value Measurements Recurring | Level 3 | Other derivative contracts
Fair value measurements
Other assets	2	1
Other liabilities	3	3
Fair Value Measurements Recurring | Netting Adjustment
Fair value measurements
Trading account assets	(454)	(493)
Total assets	(454)	(493)
Percentage of Total	(3.00%)	(3.00%)
Trading account liabilities	(510)	(423)
Total liabilities	(510)	(423)
Percentage of Total	(66.00%)	(65.00%)
Fair Value Measurements Recurring | Netting Adjustment | Interest rate derivative contracts
Fair value measurements
Trading account assets	(150)	(212)
Trading account liabilities	(408)	(379)
Fair Value Measurements Recurring | Netting Adjustment | Commodity derivative contracts
Fair value measurements
Trading account assets	(48)	(66)
Trading account liabilities	(79)	(33)
Fair Value Measurements Recurring | Netting Adjustment | Foreign exchange derivative contracts
Fair value measurements
Trading account assets	(10)	(18)
Trading account liabilities	(23)	(11)
Fair Value Measurements Recurring | Netting Adjustment | Equity Derivative contracts
Fair value measurements
Trading account assets	$ (246)	$ (197)