Securities - Available for Sale Securities (Unrealized Loss Position) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Fair value less than 12 months, total temporarily impaired securities	$ 8,693	$ 9,951	$ 1,464
Gross unrealized losses less than 12 months, total temporarily impaired securities	275	417	5
Fair value 12 months or longer, total temporarily impaired securities	880	157	3
Gross unrealized losses 12 months or longer, total temporarily impaired securities	45	11
Fair value, total temporarily impaired securities	9,573	10,108	1,467
Gross unrealized losses, total temporarily impaired securities	320	428	5
Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Fair Value less than 12 months	3,139	3,969
Held-to-maturity Securities, Gross unrealized losses, less than 12 months	92	145
Held-to-maturity Securities, Fair Value 12 months or longer	200
Held-to-maturity Securities, Gross unrealized losses, 12 months or longer	10
Held-to-maturity Securities, Fair Value	3,339	3,969
Held-to-maturity Securities, Gross unrealized losses	102	145
Other Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	1,153	856	1
Gross unrealized losses, less than 12 months	10	11
Fair value, 12 months or longer
Gross unrealized losses, 12 months or longer
Fair Value	1,153	856	1
Gross unrealized losses, Total	10	11
Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	4,401	5,122	1,443
Gross unrealized losses, less than 12 months	173	261	5
Fair value, 12 months or longer	678	157
Gross unrealized losses, 12 months or longer	35	11
Fair Value	5,079	5,279	1,443
Gross unrealized losses, Total	208	272	5
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months		2	20
Gross unrealized losses, less than 12 months
Fair value, 12 months or longer	2		3
Gross unrealized losses, 12 months or longer
Fair Value	2	2	23
Gross unrealized losses, Total
Other Securities, Held-to-Maturity [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Fair Value less than 12 months		2
Held-to-maturity Securities, Gross unrealized losses, less than 12 months
Held-to-maturity Securities, Fair Value 12 months or longer
Held-to-maturity Securities, Gross unrealized losses, 12 months or longer
Held-to-maturity Securities, Fair Value		2
Held-to-maturity Securities, Gross unrealized losses