Investments (Net Realized Gains (Losses) From Sales Of Available-For-Sale Securities) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Investments [Abstract]
Proceeds from sales	$ 187	$ 439	$ 379	$ 463
Available For Sale Securities Realized Gain Loss [Abstract]
Gross realized gains	3	55	8	57
Gross realized losses	$ (2)	$ 13	$ (9)	$ 13