Investments (Gross Realized Gains And Losses From Sales Of Available For Sale Securities) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Schedule Of Investments Available For Sale Realized Gains And Losses [Line Items]
Gross realized gains	$ 196		$ 239		$ 92
Gross realized losses	(127)		(104)		(30)
Net	$ 69	[1]	$ 135	[1]	$ 62	[1]

[1] These balances are included in the "Net gains (losses) on financial instruments at fair value and foreign exchange" line item on the Company's consolidated statements of operations.