Securities - Available for Sale Securities (Unrealized Loss Position) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Gross unrealized losses	$ 30	$ 57	$ 102
Fair value less than 12 months, total temporarily impaired securities	2,405	4,028	8,693
Gross unrealized losses less than 12 months, total temporarily impaired securities	33	63	275
Fair value 12 months or longer, total temporarily impaired securities	4,072	5,006	880
Gross unrealized losses 12 months or longer, total temporarily impaired securities	74	131	45
Fair value, total temporarily impaired securities	6,477	9,034	9,573
Gross unrealized losses, total temporarily impaired securities	107	194	320
Other Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	39		1,153
Gross unrealized losses, less than 12 months			10
Fair value, 12 months or longer		78
Gross unrealized losses, 12 months or longer		1
Fair Value	39	78	1,153
Gross unrealized losses, Total		1	10
Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	1,722	3,019	4,401
Gross unrealized losses, less than 12 months	25	52	173
Fair value, 12 months or longer	2,722	2,932	678
Gross unrealized losses, 12 months or longer	52	84	35
Fair Value	4,444	5,951	5,079
Gross unrealized losses, Total	77	136	208
Held-to-maturity Securities, Fair Value less than 12 months	637	1,005	3,139
Held-to-maturity Securities, Gross unrealized losses, less than 12 months	8	11	92
Held-to-maturity Securities, Fair Value 12 months or longer	1,348	1,994	200
Held-to-maturity Securities, Gross unrealized losses, 12 months or longer	22	46	10
Held-to-maturity Securities, Fair Value	1,985	2,999	3,339
Held-to-maturity Securities, Gross unrealized losses	30	57	102
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	3	4
Fair value, 12 months or longer	2	2	2
Fair Value	5	6	2
Held-to-maturity Securities, Fair Value less than 12 months	4
Held-to-maturity Securities, Fair Value	$ 4

Available for sale and held to maturity securities continuous unrealized loss position aggregate losses.

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Available for sale and held to maturity securities continuous unrealized loss position fair value.

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Available for sale and held to maturity securities continuous unrealized loss position less than twelve months aggregate losses.

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Available for sale and held to maturity securities continuous unrealized loss position less than twelve months fair value.

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Available for sale and held to maturity securities continuous unrealized loss position twelve months or longer aggregate losses.

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Available for sale securities and held to maturity securities continuous unrealized loss position twelve months or longer fair value.

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

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-Publisher FASB

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position.

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This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

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Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity.

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