Number of Shares Issued and Outstanding and Carrying Amount of Preferred Stock (Detail) (USD $) In Millions, except Share data, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Class of Stock [Line Items]
Shares Issued and Outstanding	159,910	[1]	72,510	[1]
Liquidation Preference	$ 4,936	[1]	$ 2,751	[1]
Discount	167	[1]	145	[1]
Carrying Amount	4,769	[1]	2,606	[1]
Series A
Class of Stock [Line Items]
Shares Issued and Outstanding	12,510		12,510
Liquidation Preference	1,251		1,251
Discount	145		145
Carrying Amount	1,106		1,106
Series B
Class of Stock [Line Items]
Shares Issued and Outstanding	40,000		40,000
Liquidation Preference	1,000		1,000
Carrying Amount	1,000		1,000
Series D
Class of Stock [Line Items]
Shares Issued and Outstanding	20,000		20,000
Liquidation Preference	500		500
Carrying Amount	500		500
Series F
Class of Stock [Line Items]
Shares Issued and Outstanding	44,000
Liquidation Preference	1,100
Discount	12
Carrying Amount	1,088
Series G
Class of Stock [Line Items]
Shares Issued and Outstanding	43,400
Liquidation Preference	1,085
Discount	10
Carrying Amount	$ 1,075

[1] The par value of all shares issued and outstanding at September 30, 2012 and December 31, 2011, was $1.00 per share.