Loans and Allowance for Loan Losses (Details 13) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Loan impairment
Recorded investment with an allowance	$ 495	$ 376
Recorded investment without an allowance	125	232
Impaired loans	620	608
Allowance for impaired loans	63	39
Unpaid principal balance with an allowance	524	399
Unpaid principal balance without an allowance	159	277
Total, excluding purchased credit impaired loans
Loan impairment
Recorded investment with an allowance	493	374
Recorded investment without an allowance	125	231
Impaired loans	618	605
Allowance for impaired loans	63	39
Unpaid principal balance with an allowance	522	397
Unpaid principal balance without an allowance	158	271
Commercial portfolio
Loan impairment
Recorded investment with an allowance	273	150
Recorded investment without an allowance	11	116
Impaired loans	284	266
Allowance for impaired loans	43	19
Unpaid principal balance with an allowance	285	157
Unpaid principal balance without an allowance	16	129
Commercial portfolio | Commercial and industrial
Loan impairment
Recorded investment with an allowance	242	117
Recorded investment without an allowance	4	104
Impaired loans	246	221
Allowance for impaired loans	40	16
Unpaid principal balance with an allowance	250	121
Unpaid principal balance without an allowance	7	114
Commercial portfolio | Commercial mortgage
Loan impairment
Recorded investment with an allowance	31	33
Recorded investment without an allowance	7	12
Impaired loans	38	45
Allowance for impaired loans	3	3
Unpaid principal balance with an allowance	35	36
Unpaid principal balance without an allowance	9	15
Consumer portfolio
Loan impairment
Recorded investment with an allowance	220	224
Recorded investment without an allowance	114	115
Impaired loans	334	339
Allowance for impaired loans	20	20
Unpaid principal balance with an allowance	237	240
Unpaid principal balance without an allowance	142	142
Consumer portfolio | Residential mortgage
Loan impairment
Recorded investment with an allowance	215	220
Recorded investment without an allowance	93	95
Impaired loans	308	315
Allowance for impaired loans	20	20
Unpaid principal balance with an allowance	231	236
Unpaid principal balance without an allowance	107	108
Consumer portfolio | Home equity and other consumer loans
Loan impairment
Recorded investment with an allowance	5	4
Recorded investment without an allowance	21	20
Impaired loans	26	24
Unpaid principal balance with an allowance	6	4
Unpaid principal balance without an allowance	35	34
Purchased credit-impaired loans
Loan impairment
Recorded investment with an allowance	2	2
Recorded investment without an allowance		1
Impaired loans	2	3
Unpaid principal balance with an allowance	2	2
Unpaid principal balance without an allowance	$ 1	$ 6