Derivatives And Hedging (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended				3 Months Ended		9 Months Ended
	Sep. 30, 2012	May 31, 2011	Sep. 30, 2012 Total Return Swap [Member] Derivative	Dec. 31, 2011 Total Return Swap [Member] Derivative	Sep. 30, 2012 Total Return Swap [Member] Non-Operating Income (Expense) [Member]	Sep. 30, 2011 Total Return Swap [Member] Non-Operating Income (Expense) [Member]	Sep. 30, 2012 Total Return Swap [Member] Non-Operating Income (Expense) [Member]	Sep. 30, 2011 Total Return Swap [Member] Non-Operating Income (Expense) [Member]
Derivative [Line Items]
Interest rate swap maturing in 2013		$ 750
Interest on this swap, fixed rate		1.03%
Interest on swap commencement and semi-annual payment dates	May 24 and November 24 of each year and commenced November 24, 2011.
Derivative, number of instruments held			11	6
Total return notional value of swaps			83	43
Notional value of forward foreign currency exchange contract	83
Credit default swap maximum risk of loss for credit protection	17
Amount of gains (losses) recognized in income on derivative instruments					$ (10)	$ 8	$ (13)	$ 6