Investment Securities (Summary) (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, amortized cost	$ 55,269,000,000	$ 43,181,000,000
Securities available for sale debt securities, unrealized gains	854,000,000	1,262,000,000
Securities available for sale debt securities, unrealized losses	(363,000,000)	(208,000,000)
Securities available for sale, fair value	55,760,000,000	44,235,000,000
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, amortized cost	54,679,000,000	42,739,000,000
Securities available for sale debt securities, unrealized gains	854,000,000	1,262,000,000
Securities available for sale debt securities, unrealized losses	(362,000,000)	(207,000,000)
Securities available for sale, fair value	55,171,000,000	43,794,000,000
Held to Maturity Securities, Amortized Cost, Total	14,768,000,000	11,588,000,000
Held-to-maturity securities, unrealized gains	311,000,000	414,000,000
Held-to-maturity securities, unrealized losses	(77,000,000)	(18,000,000)
Held-to-maturity securities, fair value	15,002,000,000	11,984,000,000
AFS to HTM Transfer Net Unrealized Gains In AOCI	97,000,000	125,000,000
US Treasury and Government Agencies Securities [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, amortized cost	9,764,000,000	5,237,000,000
Securities available for sale debt securities, unrealized gains	152,000,000	186,000,000
Securities available for sale debt securities, unrealized losses	(42,000,000)	(1,000,000)
Securities available for sale, fair value	9,874,000,000	5,422,000,000
Held to Maturity Securities, Amortized Cost, Total	258,000,000	248,000,000
Held-to-maturity securities, unrealized gains	40,000,000	44,000,000
Held-to-maturity securities, fair value	298,000,000	292,000,000
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, amortized cost	24,698,000,000	17,646,000,000
Securities available for sale debt securities, unrealized gains	250,000,000	438,000,000
Securities available for sale debt securities, unrealized losses	(128,000,000)	(41,000,000)
Securities available for sale, fair value	24,820,000,000	18,043,000,000
Held to Maturity Securities, Amortized Cost, Total	9,552,000,000	5,736,000,000
Held-to-maturity securities, unrealized gains	101,000,000	166,000,000
Held-to-maturity securities, unrealized losses	(65,000,000)	(10,000,000)
Held-to-maturity securities, fair value	9,588,000,000	5,892,000,000
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, amortized cost	3,992,000,000	4,723,000,000
Securities available for sale debt securities, unrealized gains	247,000,000	318,000,000
Securities available for sale debt securities, unrealized losses	(88,000,000)	(99,000,000)
Securities available for sale, fair value	4,151,000,000	4,942,000,000
Held to Maturity Securities, Amortized Cost, Total	233,000,000	270,000,000
Held-to-maturity securities, unrealized gains	8,000,000	13,000,000
Held-to-maturity securities, fair value	241,000,000	283,000,000
Commercial Mortgage Backed Securities [Member] | Mortgage-backed Securities Agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, amortized cost	1,917,000,000	2,178,000,000
Securities available for sale debt securities, unrealized gains	11,000,000	23,000,000
Securities available for sale debt securities, unrealized losses	(10,000,000)	(14,000,000)
Securities available for sale, fair value	1,918,000,000	2,187,000,000
Held to Maturity Securities, Amortized Cost, Total	1,128,000,000	1,200,000,000
Held-to-maturity securities, unrealized gains	40,000,000	53,000,000
Held-to-maturity securities, fair value	1,168,000,000	1,253,000,000
Commercial Mortgage Backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, amortized cost	4,902,000,000	4,085,000,000
Securities available for sale debt securities, unrealized gains	30,000,000	88,000,000
Securities available for sale debt securities, unrealized losses	(29,000,000)	(11,000,000)
Securities available for sale, fair value	4,903,000,000	4,162,000,000
Held to Maturity Securities, Amortized Cost, Total	722,000,000	1,010,000,000
Held-to-maturity securities, unrealized gains	6,000,000	19,000,000
Held-to-maturity securities, unrealized losses	(1,000,000)
Held-to-maturity securities, fair value	727,000,000	1,029,000,000
Asset Backed Securities [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, amortized cost	5,417,000,000	5,141,000,000
Securities available for sale debt securities, unrealized gains	54,000,000	78,000,000
Securities available for sale debt securities, unrealized losses	(48,000,000)	(32,000,000)
Securities available for sale, fair value	5,423,000,000	5,187,000,000
Held to Maturity Securities, Amortized Cost, Total	717,000,000	759,000,000
Held-to-maturity securities, unrealized gains		2,000,000
Held-to-maturity securities, unrealized losses	(10,000,000)	(8,000,000)
Held-to-maturity securities, fair value	707,000,000	753,000,000
State and Municipal [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, amortized cost	1,982,000,000	1,953,000,000
Securities available for sale debt securities, unrealized gains	79,000,000	88,000,000
Securities available for sale debt securities, unrealized losses	(5,000,000)	(3,000,000)
Securities available for sale, fair value	2,056,000,000	2,038,000,000
Held to Maturity Securities, Amortized Cost, Total	1,954,000,000	2,042,000,000
Held-to-maturity securities, unrealized gains	116,000,000	111,000,000
Held-to-maturity securities, fair value	2,070,000,000	2,153,000,000
Other Debt Securities [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, amortized cost	2,007,000,000	1,776,000,000
Securities available for sale debt securities, unrealized gains	31,000,000	43,000,000
Securities available for sale debt securities, unrealized losses	(12,000,000)	(6,000,000)
Securities available for sale, fair value	2,026,000,000	1,813,000,000
Held to Maturity Securities, Amortized Cost, Total	204,000,000	323,000,000
Held-to-maturity securities, unrealized gains		6,000,000
Held-to-maturity securities, unrealized losses	(1,000,000)
Held-to-maturity securities, fair value	203,000,000	329,000,000
Corporate Stocks And Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale equity securities, fair value	589,000,000	441,000,000
Securities available for sale equity securities, unrealized losses	(1,000,000)	(1,000,000)
Securities available for sale equity securities, amortized cost	$ 590,000,000	$ 442,000,000