Fair Value (Fair Value Option - Fair Value and Principal Balances) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Customer Resale Agreements [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	$ 194	$ 207
Aggregate Unpaid Principal Balance - Assets	184	196
Difference - Assets	10	11
Trading Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	14	6
Aggregate Unpaid Principal Balance - Assets	14	6
Loans Held For Sale [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	1,259	1,315
Aggregate Unpaid Principal Balance - Assets	1,198	1,280
Difference - Assets	61	35
Loans Held For Sale [Member] | Commercial Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	521	586
Aggregate Unpaid Principal Balance - Assets	605	678
Difference - Assets	(84)	(92)
Loans Held For Sale [Member] | Performing Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	1,250	1,298
Aggregate Unpaid Principal Balance - Assets	1,188	1,260
Difference - Assets	62	38
Loans Held For Sale [Member] | Performing Loans [Member] | Commercial Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	517	583
Aggregate Unpaid Principal Balance - Assets	596	669
Difference - Assets	(79)	(86)
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 - Assets	2	2
Aggregate Unpaid Principal Balance - Assets	2	2
Difference - Assets
Loans Held For Sale [Member] | Nonaccrual Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	7	15
Aggregate Unpaid Principal Balance - Assets	8	18
Difference - Assets	(1)	(3)
Loans Held For Sale [Member] | Nonaccrual Loans [Member] | Commercial Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	4	3
Aggregate Unpaid Principal Balance - Assets	9	9
Difference - Assets	(5)	(6)
Loans - Portfolio [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	884	1,025
Aggregate Unpaid Principal Balance - Assets	1,195	1,428
Difference - Assets	(311)	(403)
Loans - Portfolio [Member] | Performing Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	178	215
Aggregate Unpaid Principal Balance - Assets	262	313
Difference - Assets	(84)	(98)
Loans - Portfolio [Member] | Accruing loans 90 days or more past due | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	450	445
Aggregate Unpaid Principal Balance - Assets	529	517
Difference - Assets	(79)	(72)
Loans - Portfolio [Member] | Nonaccrual Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	256	365
Aggregate Unpaid Principal Balance - Assets	404	598
Difference - Assets	(148)	(233)
Other Borrowed Funds [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Liabilities	170	184
Aggregate Unpaid Principal Balance - Liabilities	215	225
Difference - Liabilities	$ (45)	$ (41)