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Investments (Schedule Of Cost And Fair Value Of Equity Securities) (Detail) - USD ($)
$ in Millions
Jun. 30, 2015
Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]    
Cost $ 433 $ 440
Gross unrealized appreciation 77 83
Gross unrealized depreciation (12) (13)
Fair value $ 498 $ 510