Available-for-Sale and Held-to-Maturity Securities (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011		Jun. 30, 2011
Investment Holdings [Line Items]
Total Unrealized Losses	$ (11)		$ (10)		$ (10)
Fair Value	15,552	[1]	15,362	[1]	15,502	[1]
Amortized Cost	305	[2]	322	[2]	344	[2]
Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	14,818		14,614		14,889
Unrealized Gains	745		758		623
Total Unrealized Losses	(11)		(10)		(10)
Fair Value	15,552		15,362		15,502
Held-to-maturity Securities [Member]
Investment Holdings [Line Items]
Amortized Cost	305		322		344
Fair Value	305		322		344
US Treasury and Government | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	51		171		199
Unrealized Gains					7
Fair Value	51		171		206
US Government-sponsored Enterprises Debt Securities | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	1,781		1,782		2,141
Unrealized Gains	185		180		118
Fair Value	1,966		1,962		2,259
US States and Political Subdivisions Debt Securities | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	205		96		113
Unrealized Gains	6		5		2
Fair Value	211		101		115
US States and Political Subdivisions Debt Securities | Held-to-maturity Securities [Member]
Investment Holdings [Line Items]
Amortized Cost	303		320		340
Fair Value	303		320		340
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	8,807		9,743		10,269
Unrealized Gains	477		542		475
Total Unrealized Losses	(5)		(1)		(4)
Fair Value	9,279		10,284		10,740
Other Debt Securities | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	2,743		1,792		1,135
Unrealized Gains	74		29		17
Total Unrealized Losses	(6)		(9)		(6)
Fair Value	2,811		1,812		1,146
Other Debt Securities | Held-to-maturity Securities [Member]
Investment Holdings [Line Items]
Amortized Cost	2		2		4
Fair Value	2		2		4
Equity Securities, Other | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	1,231		1,030		1,032
Unrealized Gains	3		2		4
Fair Value	$ 1,234	[3]	$ 1,032	[3]	$ 1,036	[3]

[1] Amortized cost of $14,818, $14,614 and $14,889 at June 30, 2012, December 31, 2011 and June 30, 2011, respectively.

[2] Fair value of $305, $322 and $344 at June 30, 2012, December 31, 2011 and June 30, 2011, respectively.

[3] Other securities consist of FHLB and FRB restricted stock holdings of $497 and $346, respectively, at June 30, 2012, $497 and $345, respectively, at December 31, 2011, and $497 and $344, respectively, at June 30, 2011, that are carried at cost, and certain mutual fund and equity security holdings.