Investment Securities (Contractual Maturity of Debt Securities) (Details) - USD ($)	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale, amortized cost	$ 46,902,000,000	$ 43,181,000,000
Available-for-sale Securities, Fair value, Total	47,679,000,000	44,235,000,000
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for Sale Securities, Amortized Cost, 1 year or less	750,000,000
Available for Sale Securities, Amortized Cost, After 1 year through 5 years	3,606,000,000
Available for Sale Securities, Amortized Cost, After 5 years through 10 years	7,532,000,000
Available for Sale Securities, Amortized Cost, After 10 years	34,586,000,000
Securities available for sale, amortized cost	46,474,000,000	42,739,000,000
Available-for-sale Securities, Fair value, 1 year or less	757,000,000
Available-for-sale Securities, Fair value, After 1 year through 5 years	3,682,000,000
Available-for-sale Securities, Fair value, After 5 years through 10 years	7,628,000,000
Available-for-sale Securities, Fair value, After 10 years	35,185,000,000
Available-for-sale Securities, Fair value, Total	$ 47,252,000,000	43,794,000,000
Weighted-average yield, GAAP basis, available for sale securities	2.83%
Held to Maturity Securities, Amortized Cost, After 1 year through 5 years	$ 1,011,000,000
Held to Maturity Securities, Amortized Cost, After 5 years through 10 years	2,083,000,000
Held to Maturity Securities, Amortized Cost, After 10 years	10,589,000,000
Held to Maturity Securities, Amortized Cost, Total	13,683,000,000	11,588,000,000
Held-to-maturity Securities, Fair Value, After 1 year through 5 years	1,050,000,000
Held-to-maturity Securities, Fair Value, After 5 years through 10 years	2,134,000,000
Held-to-maturity Securities, Fair Value, After 10 years	10,744,000,000
Held-to-maturity Securities, Debt Maturities, Fair Value, Total	$ 13,928,000,000	$ 11,984,000,000
Weighted-average yield, GAAP basis, held to maturity securities	3.48%
One Year or Less [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Weighted-average yield, GAAP basis, available for sale securities	2.96%
After One Year Through Five Years [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Weighted-average yield, GAAP basis, available for sale securities	2.46%
Weighted-average yield, GAAP basis, held to maturity securities	3.49%
After Five Years Through Ten Years [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Weighted-average yield, GAAP basis, available for sale securities	2.33%
Weighted-average yield, GAAP basis, held to maturity securities	3.04%
After Ten Years [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Weighted-average yield, GAAP basis, available for sale securities	2.98%
Weighted-average yield, GAAP basis, held to maturity securities	3.56%
US Treasury and Government Agencies Securities [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for Sale Securities, Amortized Cost, 1 year or less	$ 513,000,000
Available for Sale Securities, Amortized Cost, After 1 year through 5 years	804,000,000
Available for Sale Securities, Amortized Cost, After 5 years through 10 years	3,976,000,000
Available for Sale Securities, Amortized Cost, After 10 years	638,000,000
Securities available for sale, amortized cost	5,931,000,000
Held to Maturity Securities, Amortized Cost, After 10 years	253,000,000
Held to Maturity Securities, Amortized Cost, Total	253,000,000
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for Sale Securities, Amortized Cost, After 1 year through 5 years	123,000,000
Available for Sale Securities, Amortized Cost, After 5 years through 10 years	760,000,000
Available for Sale Securities, Amortized Cost, After 10 years	19,746,000,000
Securities available for sale, amortized cost	20,629,000,000
Held to Maturity Securities, Amortized Cost, After 5 years through 10 years	215,000,000
Held to Maturity Securities, Amortized Cost, After 10 years	7,984,000,000
Held to Maturity Securities, Amortized Cost, Total	8,199,000,000
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for Sale Securities, Amortized Cost, After 1 year through 5 years	5,000,000
Available for Sale Securities, Amortized Cost, After 5 years through 10 years	1,000,000
Available for Sale Securities, Amortized Cost, After 10 years	4,351,000,000
Securities available for sale, amortized cost	4,357,000,000
Held to Maturity Securities, Amortized Cost, After 10 years	252,000,000
Held to Maturity Securities, Amortized Cost, Total	252,000,000
Commercial Mortgage Backed Securities [Member] | Mortgage-backed Securities Agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for Sale Securities, Amortized Cost, 1 year or less	83,000,000
Available for Sale Securities, Amortized Cost, After 1 year through 5 years	136,000,000
Available for Sale Securities, Amortized Cost, After 5 years through 10 years	48,000,000
Available for Sale Securities, Amortized Cost, After 10 years	1,713,000,000
Securities available for sale, amortized cost	1,980,000,000
Held to Maturity Securities, Amortized Cost, After 1 year through 5 years	940,000,000
Held to Maturity Securities, Amortized Cost, After 5 years through 10 years	144,000,000
Held to Maturity Securities, Amortized Cost, After 10 years	58,000,000
Held to Maturity Securities, Amortized Cost, Total	1,142,000,000
Commercial Mortgage Backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for Sale Securities, Amortized Cost, After 1 year through 5 years	85,000,000
Available for Sale Securities, Amortized Cost, After 10 years	4,283,000,000
Securities available for sale, amortized cost	4,368,000,000
Held to Maturity Securities, Amortized Cost, After 1 year through 5 years	6,000,000
Held to Maturity Securities, Amortized Cost, After 10 years	806,000,000
Held to Maturity Securities, Amortized Cost, Total	812,000,000
Asset backed [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for Sale Securities, Amortized Cost, 1 year or less	5,000,000
Available for Sale Securities, Amortized Cost, After 1 year through 5 years	1,150,000,000
Available for Sale Securities, Amortized Cost, After 5 years through 10 years	2,104,000,000
Available for Sale Securities, Amortized Cost, After 10 years	2,118,000,000
Securities available for sale, amortized cost	5,377,000,000
Held to Maturity Securities, Amortized Cost, After 1 year through 5 years	9,000,000
Held to Maturity Securities, Amortized Cost, After 5 years through 10 years	592,000,000
Held to Maturity Securities, Amortized Cost, After 10 years	135,000,000
Held to Maturity Securities, Amortized Cost, Total	736,000,000
State and Municipal [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for Sale Securities, Amortized Cost, 1 year or less	9,000,000
Available for Sale Securities, Amortized Cost, After 1 year through 5 years	129,000,000
Available for Sale Securities, Amortized Cost, After 5 years through 10 years	316,000,000
Available for Sale Securities, Amortized Cost, After 10 years	1,556,000,000
Securities available for sale, amortized cost	2,010,000,000
Held to Maturity Securities, Amortized Cost, After 1 year through 5 years	56,000,000
Held to Maturity Securities, Amortized Cost, After 5 years through 10 years	825,000,000
Held to Maturity Securities, Amortized Cost, After 10 years	1,101,000,000
Held to Maturity Securities, Amortized Cost, Total	1,982,000,000
Other Debt Securities [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for Sale Securities, Amortized Cost, 1 year or less	140,000,000
Available for Sale Securities, Amortized Cost, After 1 year through 5 years	1,174,000,000
Available for Sale Securities, Amortized Cost, After 5 years through 10 years	327,000,000
Available for Sale Securities, Amortized Cost, After 10 years	181,000,000
Securities available for sale, amortized cost	1,822,000,000
Held to Maturity Securities, Amortized Cost, After 5 years through 10 years	307,000,000
Held to Maturity Securities, Amortized Cost, Total	$ 307,000,000