Investment Securities - Investment Securities Available for Sale (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	$ 40,006		$ 39,040
Available-for-sale securities, Unrealized Gains	787		1,246
Available-for-sale securities, Unrealized Losses Other-than-Temporary	(16)		(36)
Available-for-sale securities, Unrealized Losses Other	(470)		(111)
Available-for-sale securities, Fair Value	40,307	[1]	40,139	[1]
U.S. Treasury and agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	1,582		1,211
Available-for-sale securities, Unrealized Gains	7		16
Available-for-sale securities, Unrealized Losses Other	(38)		(1)
Available-for-sale securities, Fair Value	1,551		1,226
Collateralized Debt/Loan Obligation Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	19		32
Available-for-sale securities, Unrealized Gains	6		10
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	599		579
Available-for-sale securities, Unrealized Gains	14		14
Available-for-sale securities, Unrealized Losses Other	(1)		(1)
Available-for-sale securities, Fair Value	612		592
Obligations of state and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	5,779		6,059
Available-for-sale securities, Unrealized Gains	198		396
Available-for-sale securities, Unrealized Losses Other	(32)
Available-for-sale securities, Fair Value	5,945		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, Fair Value	6		6
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	789		814
Available-for-sale securities, Unrealized Gains			2
Available-for-sale securities, Unrealized Losses Other	(82)		(85)
Available-for-sale securities, Fair Value	707		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	29		27
Available-for-sale securities, Unrealized Losses Other	(15)		(14)
Available-for-sale securities, Fair Value	219		218
Other Investment [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	219		182
Available-for-sale securities, Unrealized Gains	24		20
Available-for-sale securities, Fair Value	243		202
Agency [Member] | Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	29,762		28,754
Available-for-sale securities, Unrealized Gains	492		746
Available-for-sale securities, Unrealized Losses Other	(298)		(5)
Available-for-sale securities, Fair Value	29,956		29,495
Agency [Member] | Commercial [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	172		185
Available-for-sale securities, Unrealized Gains	5		8
Available-for-sale securities, Fair Value	177		193
Residential Non-Agency Prime [Member] | Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	556		641
Available-for-sale securities, Unrealized Gains	5		3
Available-for-sale securities, Unrealized Losses Other-than-Temporary	(10)		(16)
Available-for-sale securities, Unrealized Losses Other	(4)		(4)
Available-for-sale securities, Fair Value	547		624
Residential Non-Agency Non-Prime [Member] | Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	318		372
Available-for-sale securities, Unrealized Gains	7		4
Available-for-sale securities, Unrealized Losses Other-than-Temporary	(6)		(20)
Available-for-sale securities, Unrealized Losses Other			(1)
Available-for-sale securities, Fair Value	$ 319		$ 355

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