Securities - Available for Sale Securities (Unrealized Loss Position) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Gross unrealized losses	$ 57	$ 145
Fair value less than 12 months, total temporarily impaired securities	4,028	9,951
Gross unrealized losses less than 12 months, total temporarily impaired securities	63	417
Fair value 12 months or longer, total temporarily impaired securities	5,006	157
Gross unrealized losses 12 months or longer, total temporarily impaired securities	131	11
Fair value, total temporarily impaired securities	9,034	10,108
Gross unrealized losses, total temporarily impaired securities	194	428
Other Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months		856
Gross unrealized losses, less than 12 months		11
Fair value, 12 months or longer	78
Gross unrealized losses, 12 months or longer	1
Fair Value	78	856
Gross unrealized losses, Total	1	11
Held-to-maturity Securities, Gross unrealized losses
Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	3,019	5,122
Gross unrealized losses, less than 12 months	52	261
Fair value, 12 months or longer	2,932	157
Gross unrealized losses, 12 months or longer	84	11
Fair Value	5,951	5,279
Gross unrealized losses, Total	136	272
Held-to-maturity Securities, Fair Value less than 12 months	1,005	3,969
Held-to-maturity Securities, Gross unrealized losses, less than 12 months	11	145
Held-to-maturity Securities, Fair Value 12 months or longer	1,994
Held-to-maturity Securities, Gross unrealized losses, 12 months or longer	46
Held-to-maturity Securities, Fair Value	2,999	3,969
Held-to-maturity Securities, Gross unrealized losses	57	145
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	4	2
Gross unrealized losses, less than 12 months
Fair value, 12 months or longer	2
Gross unrealized losses, 12 months or longer
Fair Value	6	2
Gross unrealized losses, Total
Held-to-maturity Securities, Fair Value less than 12 months		2
Held-to-maturity Securities, Fair Value		2
Held-to-maturity Securities, Gross unrealized losses

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 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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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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