Available-for-Sale and Held-to-Maturity Securities (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011		Sep. 30, 2011
Investment Holdings [Line Items]
Amortized Cost	$ 14,641		$ 14,614		$ 15,427
Total Unrealized Losses	(14)		(10)		(12)
Fair Value	15,402	[1]	15,362	[1]	16,227	[1]
Amortized Cost	287	[2]	322	[2]	337	[2]
Fair Value	287		322		337
Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	14,641		14,614		15,427
Unrealized Gains	775		758		812
Total Unrealized Losses	(14)		(10)		(12)
Fair Value	15,402		15,362		16,227
Held-to-maturity Securities [Member]
Investment Holdings [Line Items]
Amortized Cost	287		322		337
Fair Value	287		322		337
US Treasury and Government | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	41		171		201
Unrealized Gains					1
Fair Value	41		171		202
US Government-sponsored Enterprises Debt Securities | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	1,730		1,782		1,808
Unrealized Gains	192		180		182
Fair Value	1,922		1,962		1,990
US States and Political Subdivisions Debt Securities | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	203		96		101
Unrealized Gains	8		5		4
Fair Value	211		101		105
US States and Political Subdivisions Debt Securities | Held-to-maturity Securities [Member]
Investment Holdings [Line Items]
Amortized Cost	285		320		335
Fair Value	285		320		335
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	8,534		9,743		10,413
Unrealized Gains	461		542		605
Total Unrealized Losses	(9)		(1)		(1)
Fair Value	8,986		10,284		11,017
Other Debt Securities | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	3,055		1,792		1,567
Unrealized Gains	114		29		17
Total Unrealized Losses	(5)		(9)		(11)
Fair Value	3,164		1,812		1,573
Other Debt Securities | Held-to-maturity Securities [Member]
Investment Holdings [Line Items]
Amortized Cost	2		2		2
Fair Value	2		2		2
Equity Securities, Other | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	1,078	[3]	1,030	[3]	1,337	[3]
Unrealized Gains			2	[3]	3	[3]
Fair Value	$ 1,078	[3]	$ 1,032	[3]	$ 1,340	[3]

[1] Amortized cost of $14,641, $14,614 and $15,427 at September 30, 2012, December 31, 2011 and September 30, 2011, respectively.

[2] Fair value of $287, $322 and $337 at September 30, 2012, December 31, 2011 and September 30, 2011, respectively.

[3] Other securities consist of FHLB and FRB restricted stock holdings of $497 and $346, respectively, at September 30, 2012, and $497 and $345, respectively, at December 31, 2011 and September 30, 2011, that are carried at cost, and certain mutual fund and equity security holdings.