Securities with Unrealized Losses, Aggregated by Category and Period of Continuous Unrealized Loss (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Investment [Line Items]
Securities available for sale Less than 12 months Fair Value	$ 1,474		$ 11,094
Securities available for sale Less than 12 months Unrealized Losses	3		57
Securities available for sale 12 months or longer Fair Value	1,875		898
Securities available for sale 12 months or longer Unrealized Losses	85		216
Total Securities available for sale with unrealized losses Total Fair Value	3,349		11,992
Total Securities available for sale with unrealized losses Total Unrealized Losses	88		273
Securities held to maturity Less than 12 months Fair Value	249		384
Securities held to maturity Less than 12 months Unrealized Losses	1		2
Securities held to maturity 12 months or longer Fair Value
Securities held to maturity 12 months or longer Unrealized Losses
Total Securities held to maturity with unrealized losses Total Fair Value	249		384
Total Securities held to maturity with unrealized losses Total Unrealized Losses	1		2
Securities Less than 12 months Fair Value	1,723	[1]	11,478	[2]
Securities Less than 12 months Unrealized Losses	4	[1]	59	[2]
Securities 12 months or longer Fair Value	1,875	[1]	898	[2]
Securities 12 months or longer Unrealized Losses	85	[1]	216	[2]
Total securities with unrealized losses Total Fair Value	3,598	[1]	12,376	[2]
Total securities with unrealized losses Total Unrealized Losses	89	[1]	275	[2]
U.S. agency residential mortgage-backed securities
Investment [Line Items]
Securities available for sale Less than 12 months Fair Value			5,551
Securities available for sale Less than 12 months Unrealized Losses			14
Securities available for sale 12 months or longer Fair Value	346
Securities available for sale 12 months or longer Unrealized Losses	6
Total Securities available for sale with unrealized losses Total Fair Value	346		5,551
Total Securities available for sale with unrealized losses Total Unrealized Losses	6		14
Securities held to maturity Less than 12 months Fair Value	249		384
Securities held to maturity Less than 12 months Unrealized Losses	1		2
Securities held to maturity 12 months or longer Fair Value
Securities held to maturity 12 months or longer Unrealized Losses
Total Securities held to maturity with unrealized losses Total Fair Value	249		384
Total Securities held to maturity with unrealized losses Total Unrealized Losses	1		2
Non-agency residential mortgage-backed securities
Investment [Line Items]
Securities available for sale Less than 12 months Fair Value			121
Securities available for sale Less than 12 months Unrealized Losses			8
Securities available for sale 12 months or longer Fair Value	606		746
Securities available for sale 12 months or longer Unrealized Losses	77		215
Total Securities available for sale with unrealized losses Total Fair Value	606		867
Total Securities available for sale with unrealized losses Total Unrealized Losses	77		223
Corporate debt securities
Investment [Line Items]
Securities available for sale Less than 12 months Fair Value	776		1,888
Securities available for sale Less than 12 months Unrealized Losses	1		26
Total Securities available for sale with unrealized losses Total Fair Value	776		1,888
Total Securities available for sale with unrealized losses Total Unrealized Losses	1		26
Certificates of deposit
Investment [Line Items]
Securities available for sale Less than 12 months Fair Value	698		2,158
Securities available for sale Less than 12 months Unrealized Losses	2		3
Total Securities available for sale with unrealized losses Total Fair Value	698		2,158
Total Securities available for sale with unrealized losses Total Unrealized Losses	2		3
Asset-backed and other securities
Investment [Line Items]
Securities available for sale Less than 12 months Fair Value			1,376
Securities available for sale Less than 12 months Unrealized Losses			6
Securities available for sale 12 months or longer Fair Value	923		152
Securities available for sale 12 months or longer Unrealized Losses	2		1
Total Securities available for sale with unrealized losses Total Fair Value	923		1,528
Total Securities available for sale with unrealized losses Total Unrealized Losses	$ 2		$ 7

[1] The number of investment positions with unrealized losses totaled 128 for securities available for sale and 7 for securities held to maturity.

[2] The number of investment positions with unrealized losses totaled 296 for securities available for sale and 3 for securities held to maturity.