Fair Value (Fair Value Option - Fair Value and Principal Balances) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Customer Resale Agreements [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	$ 210	$ 256
Aggregate Unpaid Principal Balance	196	237
Difference	14	19
Trading Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	21	76
Aggregate Unpaid Principal Balance	22	76
Difference	(1)
Loans Held For Sale [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	2,246	2,096
Aggregate Unpaid Principal Balance	2,267	2,021
Difference	(21)	75
Loans Held For Sale [Member] | Commercial Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	635	772
Aggregate Unpaid Principal Balance	746	901
Difference	(111)	(129)
Loans Held For Sale [Member] | Performing Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	2,200	2,072
Aggregate Unpaid Principal Balance	2,196	1,971
Difference	4	101
Loans Held For Sale [Member] | Performing Loans [Member] | Commercial Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	632	766
Aggregate Unpaid Principal Balance	739	889
Difference	(107)	(123)
Loans Held For Sale [Member] | Accruing loans 90 days or more past due | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	5	8
Aggregate Unpaid Principal Balance	4	14
Difference	1	(6)
Loans Held For Sale [Member] | Nonaccrual Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	41	16
Aggregate Unpaid Principal Balance	67	36
Difference	(26)	(20)
Loans Held For Sale [Member] | Nonaccrual Loans [Member] | Commercial Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	3	6
Aggregate Unpaid Principal Balance	7	12
Difference	(4)	(6)
Loans - Portfolio [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	811	244
Aggregate Unpaid Principal Balance	1,347	464
Difference	(536)	(220)
Loans - Portfolio [Member] | Performing Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	179	58
Aggregate Unpaid Principal Balance	282	116
Difference	(103)	(58)
Loans - Portfolio [Member] | Accruing loans 90 days or more past due | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	331	116
Aggregate Unpaid Principal Balance	535	141
Difference	(204)	(25)
Loans - Portfolio [Member] | Nonaccrual Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	301	70
Aggregate Unpaid Principal Balance	530	207
Difference	(229)	(137)
Other Borrowed Funds [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value	195
Aggregate Unpaid Principal Balance	344
Difference	$ (149)