Available-for-Sale and Held-to-Maturity Securities (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Investment Holdings
Amortized Cost	$ 17,665		$ 14,571
Total Unrealized Losses	(42)		(21)
Available for sale securities	18,080	[1]	15,207	[1]
Amortized Cost	265	[2]	284	[2]
Held-to-maturity securities	265		284
Available-for-sale Securities
Investment Holdings
Amortized Cost	17,665		14,571
Unrealized Gains	457		657
Total Unrealized Losses	(42)		(21)
Available for sale securities	18,080		15,207
Held-to-maturity Securities
Investment Holdings
Amortized Cost	265		284
Held-to-maturity securities	265		284
US Treasury and Government | Available-for-sale Securities
Investment Holdings
Amortized Cost	26		41
Available for sale securities	26		41
US Government-sponsored Enterprises Debt Securities | Available-for-sale Securities
Investment Holdings
Amortized Cost	1,524		1,730
Unrealized Gains	129		181
Available for sale securities	1,653		1,911
US States and Political Subdivisions Debt Securities | Available-for-sale Securities
Investment Holdings
Amortized Cost	201		203
Unrealized Gains	4		9
Available for sale securities	205		212
US States and Political Subdivisions Debt Securities | Held-to-maturity Securities
Investment Holdings
Amortized Cost	264		282
Held-to-maturity securities	264		282
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises
Investment Holdings
Total Unrealized Losses	(25)		(18)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises | Available-for-sale Securities
Investment Holdings
Amortized Cost	11,149	[3]	8,403	[3]
Unrealized Gains	229	[3]	345	[3]
Total Unrealized Losses	(25)	[3]	(18)	[3]
Available for sale securities	11,353	[3]	8,730	[3]
Other Debt Securities
Investment Holdings
Total Unrealized Losses	(16)		(3)
Other Debt Securities | Available-for-sale Securities
Investment Holdings
Amortized Cost	3,773		3,161
Unrealized Gains	82		119
Total Unrealized Losses	(16)		(3)
Available for sale securities	3,839		3,277
Other Debt Securities | Held-to-maturity Securities
Investment Holdings
Amortized Cost	1		2
Held-to-maturity securities	1		2
Other Debt And Equity Securities [Member]
Investment Holdings
Total Unrealized Losses	(1)
Other Debt And Equity Securities [Member] | Available-for-sale Securities
Investment Holdings
Amortized Cost	992	[4]	1,033	[4]
Unrealized Gains	13	[4]	3	[4]
Total Unrealized Losses	(1)	[4]
Available for sale securities	$ 1,004	[4]	$ 1,036	[4]

[1] Amortized cost of $17,665 and $14,571 at September 30, 2013 and December 31, 2012, respectively.

[2] Fair value of $265 and $284 at September 30, 2013 and December 31, 2012, respectively.

[3] Includes interest-only mortgage backed securities of $279 and $408 as of September 30, 2013 and December 31, 2012, respectively, recorded at fair value with fair value changes recorded in securities gains, net and securities gains, net-non-qualifying hedges on mortgage servicing rights in the Condensed Consolidated Statements of Income.

[4] Other securities consist of FHLB and FRB restricted stock holdings of $497 and $349, respectively, at September 30, 2013 and $497 and $347, respectively, at December 31, 2012, that are carried at cost, and certain mutual fund and equity security holdings.