Fair Value (Fair Value Option - Fair Value and Principal Balances) (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Customer Resale Agreements [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	$ 137,000,000	$ 155,000,000
Aggregate Unpaid Principal Balance - Assets	133,000,000	148,000,000
Difference - Assets	4,000,000	7,000,000
Loans Held For Sale [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	843,000,000	1,261,000,000
Aggregate Unpaid Principal Balance - Assets	816,000,000	1,202,000,000
Difference - Assets	27,000,000	59,000,000
Loans Held For Sale [Member] | Commercial Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	641,000,000	893,000,000
Aggregate Unpaid Principal Balance - Assets	662,000,000	972,000,000
Difference - Assets	(21,000,000)	(79,000,000)
Loans Held For Sale [Member] | Performing Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	832,000,000	1,236,000,000
Aggregate Unpaid Principal Balance - Assets	804,000,000	1,176,000,000
Difference - Assets	28,000,000	60,000,000
Loans Held For Sale [Member] | Performing Loans [Member] | Commercial Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	639,000,000	873,000,000
Aggregate Unpaid Principal Balance - Assets	659,000,000	908,000,000
Difference - Assets	(20,000,000)	(35,000,000)
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	4,000,000	9,000,000
Aggregate Unpaid Principal Balance - Assets	4,000,000	9,000,000
Loans Held For Sale [Member] | Nonaccrual Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	7,000,000	16,000,000
Aggregate Unpaid Principal Balance - Assets	8,000,000	17,000,000
Difference - Assets	(1,000,000)	(1,000,000)
Loans Held For Sale [Member] | Nonaccrual Loans [Member] | Commercial Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	2,000,000	20,000,000
Aggregate Unpaid Principal Balance - Assets	3,000,000	64,000,000
Difference - Assets	(1,000,000)	(44,000,000)
Loans - Portfolio [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	905,000,000	1,034,000,000
Aggregate Unpaid Principal Balance - Assets	1,099,000,000	1,278,000,000
Difference - Assets	(194,000,000)	(244,000,000)
Loans - Portfolio [Member] | Performing Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	204,000,000	194,000,000
Aggregate Unpaid Principal Balance - Assets	260,000,000	256,000,000
Difference - Assets	(56,000,000)	(62,000,000)
Loans - Portfolio [Member] | Accruing loans 90 days or more past due | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	475,000,000	570,000,000
Aggregate Unpaid Principal Balance - Assets	478,000,000	573,000,000
Difference - Assets	(3,000,000)	(3,000,000)
Loans - Portfolio [Member] | Nonaccrual Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	226,000,000	270,000,000
Aggregate Unpaid Principal Balance - Assets	361,000,000	449,000,000
Difference - Assets	(135,000,000)	(179,000,000)
Other Assets [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Assets	164,000,000	37,000,000
Aggregate Unpaid Principal Balance - Assets	159,000,000	37,000,000
Difference - Assets	5,000,000
Other Borrowed Funds [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value - Liabilities	93,000,000	273,000,000
Aggregate Unpaid Principal Balance - Liabilities	95,000,000	312,000,000
Difference - Liabilities	$ (2,000,000)	$ (39,000,000)