Investment Securities - Investment Securities Available for Sale (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	$ 39,240		$ 39,040
Available-for-sale securities, Unrealized Gains	691		1,246
Available-for-sale securities, Unrealized Losses Other-than-Temporary	(16)		(36)
Available-for-sale securities, Unrealized Losses Other	(608)		(111)
Available-for-sale securities, Fair Value	39,307	[1]	40,139	[1]
U.S. Treasury and agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	1,567		1,211
Available-for-sale securities, Unrealized Gains	5		16
Available-for-sale securities, Unrealized Losses Other-than-Temporary
Available-for-sale securities, Unrealized Losses Other	(51)		(1)
Available-for-sale securities, Fair Value	1,521		1,226
Collateralized Debt/Loan Obligation Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	20		32
Available-for-sale securities, Unrealized Gains	5		10
Available-for-sale securities, Unrealized Losses Other-than-Temporary
Available-for-sale securities, Unrealized Losses Other
Available-for-sale securities, Fair Value	25		42
Asset Backed Securities Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	598		579
Available-for-sale securities, Unrealized Gains	13		14
Available-for-sale securities, Unrealized Losses Other-than-Temporary
Available-for-sale securities, Unrealized Losses Other	(1)		(1)
Available-for-sale securities, Fair Value	610		592
Obligations of state and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	5,732		6,059
Available-for-sale securities, Unrealized Gains	134		396
Available-for-sale securities, Unrealized Losses Other-than-Temporary
Available-for-sale securities, Unrealized Losses Other	(46)
Available-for-sale securities, Fair Value	5,820		6,455
Obligations of foreign governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	6		6
Available-for-sale securities, Unrealized Gains
Available-for-sale securities, Unrealized Losses Other-than-Temporary
Available-for-sale securities, Unrealized Losses Other
Available-for-sale securities, Fair Value	6		6
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	734		814
Available-for-sale securities, Unrealized Gains			2
Available-for-sale securities, Unrealized Losses Other-than-Temporary
Available-for-sale securities, Unrealized Losses Other	(92)		(85)
Available-for-sale securities, Fair Value	642		731
Perpetual preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	205		205
Available-for-sale securities, Unrealized Gains	24		27
Available-for-sale securities, Unrealized Losses Other-than-Temporary
Available-for-sale securities, Unrealized Losses Other	(20)		(14)
Available-for-sale securities, Fair Value	209		218
Other Investment [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	257		182
Available-for-sale securities, Unrealized Gains	25		20
Available-for-sale securities, Unrealized Losses Other-than-Temporary
Available-for-sale securities, Unrealized Losses Other
Available-for-sale securities, Fair Value	282		202
Agency [Member] | Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	29,136		28,754
Available-for-sale securities, Unrealized Gains	476		746
Available-for-sale securities, Unrealized Losses Other-than-Temporary
Available-for-sale securities, Unrealized Losses Other	(392)		(5)
Available-for-sale securities, Fair Value	29,220		29,495
Agency [Member] | Commercial [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	165		185
Available-for-sale securities, Unrealized Gains	4		8
Available-for-sale securities, Unrealized Losses Other-than-Temporary
Available-for-sale securities, Unrealized Losses Other
Available-for-sale securities, Fair Value	169		193
Residential Non-Agency Prime [Member] | Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	513		641
Available-for-sale securities, Unrealized Gains	2		3
Available-for-sale securities, Unrealized Losses Other-than-Temporary	(10)		(16)
Available-for-sale securities, Unrealized Losses Other	(5)		(4)
Available-for-sale securities, Fair Value	500		624
Residential Non-Agency Non-Prime [Member] | Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	307		372
Available-for-sale securities, Unrealized Gains	3		4
Available-for-sale securities, Unrealized Losses Other-than-Temporary	(6)		(20)
Available-for-sale securities, Unrealized Losses Other	(1)		(1)
Available-for-sale securities, Fair Value	$ 303		$ 355

[1] Includes only collateral pledged by the Company where counterparties have the right to sell or pledge the collateral.