Available-for-Sale and Held-to-Maturity Securities (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011		Mar. 31, 2011
Investment Holdings [Line Items]
Amortized Cost	$ 15,341		$ 14,614		$ 14,707
Total Unrealized Losses			(10)		(54)
Fair Value	16,093	[1]	15,362	[1]	15,135	[1]
Amortized Cost	321	[2]	322	[2]	346	[2]
Fair Value	321		322		346
Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	15,341		14,614		14,707
Unrealized Gains	758		758		482
Total Unrealized Losses	(6)		(10)		(54)
Fair Value	16,093		15,362		15,135
Held-to-maturity Securities [Member]
Investment Holdings [Line Items]
Amortized Cost	321		322		346
Fair Value	321		322		346
US Treasury and Government | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	51		171		225
Unrealized Gains					3
Fair Value	51		171		228
US Government-sponsored Enterprises Debt Securities | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	1,782		1,782		1,669
Unrealized Gains	172		180		70
Fair Value	1,954		1,962		1,739
US States and Political Subdivisions Debt Securities | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	210		96		152
Unrealized Gains	4		5		1
Fair Value	214		101		153
US States and Political Subdivisions Debt Securities | Held-to-maturity Securities [Member]
Investment Holdings [Line Items]
Amortized Cost	319		320		341
Fair Value	319		320		341
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	9,834		9,743		10,439
Unrealized Gains	525		542		385
Total Unrealized Losses	(1)		(1)		(39)
Fair Value	10,358		10,284		10,785
Other Debt Securities | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	2,315		1,792		1,177
Unrealized Gains	55		29		20
Total Unrealized Losses	(5)		(9)		(14)
Fair Value	2,365		1,812		1,183
Other Debt Securities | Held-to-maturity Securities [Member]
Investment Holdings [Line Items]
Amortized Cost	2		2		5
Fair Value	2		2		5
Equity Securities, Other | Available-for-sale Securities
Investment Holdings [Line Items]
Amortized Cost	1,149		1,030		1,045
Unrealized Gains	2		2		3
Total Unrealized Losses					(1)
Fair Value	$ 1,151	[3]	$ 1,032		$ 1,047

[1] Amortized cost of $15,341, $14,614 and $14,707 at March 31, 2012, December 31, 2011 and March 31, 2011, respectively.

[2] Fair value of $321, $322 and $346 at March 31, 2012, December 31, 2011 and March 31, 2011, respectively.

[3] Other securities consist of FHLB and FRB restricted stock holdings of $497 and $345, respectively, at March 31, 2012 and December 31, 2011, and $524 and $344, respectively, at March 31, 2011, that are carried at cost, and certain mutual fund and equity security holdings.