Investments (Schedule Of Cost And Fair Value Of Equity Securities) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Investments, Debt and Equity Securities [Abstract]
Cost	$ 707	$ 671
Gross unrealized appreciation	41	18
Gross unrealized depreciation	(4)	(42)
Fair value	$ 744	$ 647

Amount of equity securities categorized neither as held-to-maturity nor as trading.

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