Investment Securities (Gross Unrealized Loss and Fair Value of Securities Available for Sale) (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	$ (216,000,000)	$ (22,000,000)
Unrealized loss position less than 12 months - fair value	25,715,000,000	5,223,000,000
Unrealized loss position 12 months or more - unrealized loss	(147,000,000)	(186,000,000)
Unrealized loss position 12 months or more - fair value	4,425,000,000	5,518,000,000
Total unrealized loss	(363,000,000)	(208,000,000)
Total fair value	30,140,000,000	10,741,000,000
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(216,000,000)	(22,000,000)
Unrealized loss position less than 12 months - fair value	25,669,000,000	5,223,000,000
Unrealized loss position 12 months or more - unrealized loss	(146,000,000)	(185,000,000)
Unrealized loss position 12 months or more - fair value	4,410,000,000	5,503,000,000
Total unrealized loss	(362,000,000)	(207,000,000)
Total fair value	30,079,000,000	10,726,000,000
US Treasury and Government Agencies Securities [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(40,000,000)	(1,000,000)
Unrealized loss position less than 12 months - fair value	5,885,000,000	1,426,000,000
Unrealized loss position 12 months or more - unrealized loss	(2,000,000)
Unrealized loss position 12 months or more - fair value	120,000,000
Total unrealized loss	(42,000,000)	(1,000,000)
Total fair value	6,005,000,000	1,426,000,000
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(103,000,000)	(4,000,000)
Unrealized loss position less than 12 months - fair value	11,799,000,000	644,000,000
Unrealized loss position 12 months or more - unrealized loss	(25,000,000)	(37,000,000)
Unrealized loss position 12 months or more - fair value	1,094,000,000	1,963,000,000
Total unrealized loss	(128,000,000)	(41,000,000)
Total fair value	12,893,000,000	2,607,000,000
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(3,000,000)	(5,000,000)
Unrealized loss position less than 12 months - fair value	368,000,000	276,000,000
Unrealized loss position 12 months or more - unrealized loss	(85,000,000)	(94,000,000)
Unrealized loss position 12 months or more - fair value	1,527,000,000	1,487,000,000
Total unrealized loss	(88,000,000)	(99,000,000)
Total fair value	1,895,000,000	1,763,000,000
Commercial Mortgage Backed Securities [Member] | Mortgage-backed Securities Agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(7,000,000)	(2,000,000)
Unrealized loss position less than 12 months - fair value	745,000,000	681,000,000
Unrealized loss position 12 months or more - unrealized loss	(3,000,000)	(12,000,000)
Unrealized loss position 12 months or more - fair value	120,000,000	322,000,000
Total unrealized loss	(10,000,000)	(14,000,000)
Total fair value	865,000,000	1,003,000,000
Commercial Mortgage Backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(22,000,000)	(4,000,000)
Unrealized loss position less than 12 months - fair value	2,310,000,000	928,000,000
Unrealized loss position 12 months or more - unrealized loss	(7,000,000)	(7,000,000)
Unrealized loss position 12 months or more - fair value	807,000,000	335,000,000
Total unrealized loss	(29,000,000)	(11,000,000)
Total fair value	3,117,000,000	1,263,000,000
Asset backed [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(30,000,000)	(4,000,000)
Unrealized loss position less than 12 months - fair value	3,477,000,000	913,000,000
Unrealized loss position 12 months or more - unrealized loss	(18,000,000)	(28,000,000)
Unrealized loss position 12 months or more - fair value	494,000,000	1,133,000,000
Total unrealized loss	(48,000,000)	(32,000,000)
Total fair value	3,971,000,000	2,046,000,000
State and Municipal [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(3,000,000)	(500,000)
Unrealized loss position less than 12 months - fair value	326,000,000	41,000,000
Unrealized loss position 12 months or more - unrealized loss	(2,000,000)	(3,000,000)
Unrealized loss position 12 months or more - fair value	60,000,000	77,000,000
Total unrealized loss	(5,000,000)	(3,000,000)
Total fair value	386,000,000	118,000,000
Other Debt Securities [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(8,000,000)	(2,000,000)
Unrealized loss position less than 12 months - fair value	759,000,000	314,000,000
Unrealized loss position 12 months or more - unrealized loss	(4,000,000)	(4,000,000)
Unrealized loss position 12 months or more - fair value	188,000,000	186,000,000
Total unrealized loss	(12,000,000)	(6,000,000)
Total fair value	947,000,000	500,000,000
Corporate Stocks And Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position less than 12 months - unrealized loss	(500,000)
Unrealized loss position less than 12 months - fair value	46,000,000
Unrealized loss position 12 months or more - unrealized loss	(1,000,000)	(1,000,000)
Unrealized loss position 12 months or more - fair value	15,000,000	15,000,000
Total unrealized loss	(1,000,000)	(1,000,000)
Total fair value	$ 61,000,000	$ 15,000,000