Fair Value (Fair Value Option - Fair Value and Principal Balances) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Customer Resale Agreements [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	$ 191	$ 207
Aggregate Unpaid Principal Balance - Assets	183	196
Difference - Assets	8	11
Trading Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	35	6
Aggregate Unpaid Principal Balance - Assets	35	6
Loans Held For Sale [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	1,187	1,315
Aggregate Unpaid Principal Balance - Assets	1,139	1,280
Difference - Assets	48	35
Loans Held For Sale [Member] | Commercial Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	867	586
Aggregate Unpaid Principal Balance - Assets	946	678
Difference - Assets	(79)	(92)
Loans Held For Sale [Member] | Performing Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	1,174	1,298
Aggregate Unpaid Principal Balance - Assets	1,125	1,260
Difference - Assets	49	38
Loans Held For Sale [Member] | Performing Loans [Member] | Commercial Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	865	583
Aggregate Unpaid Principal Balance - Assets	943	669
Difference - Assets	(78)	(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	4	2
Aggregate Unpaid Principal Balance - Assets	4	2
Loans Held For Sale [Member] | Nonaccrual Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	9	15
Aggregate Unpaid Principal Balance - Assets	10	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	2	3
Aggregate Unpaid Principal Balance - Assets	3	9
Difference - Assets	(1)	(6)
Loans - Portfolio [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	1,017	1,150
Aggregate Unpaid Principal Balance - Assets	1,304	1,556
Difference - Assets	(287)	(406)
Loans - Portfolio [Member] | Performing Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	205	233
Aggregate Unpaid Principal Balance - Assets	289	332
Difference - Assets	(84)	(99)
Loans - Portfolio [Member] | Accruing loans 90 days or more past due | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	551	552
Aggregate Unpaid Principal Balance - Assets	551	626
Difference - Assets		(74)
Loans - Portfolio [Member] | Nonaccrual Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	261	365
Aggregate Unpaid Principal Balance - Assets	464	598
Difference - Assets	(203)	(233)
Other Borrowed Funds [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Liabilities	274	309
Aggregate Unpaid Principal Balance - Liabilities	319	353
Difference - Liabilities	$ (45)	$ (44)