Available-for-Sale and Held-to-Maturity Securities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Investment Holdings [Line Items]
Amortized Cost	$ 14,614		$ 14,919
Unrealized Gains	758		542
Total Unrealized Losses	(10)		(47)
Fair Value	15,362	[1]	15,414	[1]
Amortized Cost	322	[2]	353	[2]
Fair Value	322		353
US Treasury and Government
Investment Holdings [Line Items]
Amortized Cost	171		225
Unrealized Gains			5
Fair Value	171		230
US Government-sponsored Enterprises Debt Securities
Investment Holdings [Line Items]
Amortized Cost	1,782		1,564
Unrealized Gains	180		81
Fair Value	1,962		1,645
US States and Political Subdivisions Debt Securities
Investment Holdings [Line Items]
Amortized Cost	96		170
Unrealized Gains	5		2
Fair Value	101		172
Amortized Cost	320		348
Fair Value	320		348
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises
Investment Holdings [Line Items]
Amortized Cost	9,743		10,570
Unrealized Gains	542		435
Total Unrealized Losses	(1)		(32)
Fair Value	10,284		10,973
Other Debt Securities
Investment Holdings [Line Items]
Amortized Cost	1,792		1,338
Unrealized Gains	29		19
Total Unrealized Losses	(9)		(15)
Fair Value	1,812		1,342
Amortized Cost	2		5
Fair Value	2		5
Equity Securities, Other
Investment Holdings [Line Items]
Amortized Cost	1,030		1,052
Unrealized Gains	2
Fair Value	$ 1,032	[3]	$ 1,052	[3]

[1] Amortized cost of $14,614 and $14,919 at December 31, 2011 and 2010 respectively.

[2] Fair value of $322 and $353 at December 31, 2011 and 2010, respectively.

[3] Other securities consist of FHLB and FRB restricted stock holdings of $497 and $345, respectively, at December 31, 2011 and, $524 and $344, respectively, at December 31, 2010, that are carried at cost, and certain mutual fund and equity security holdings.