Earnings Per Share (EPS) And Dividends (Basic And Diluted Earnings Per Share Computation) (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0.3		0.3	0.3
Net Income (Loss)	$ 109	$ 187	$ 223	$ 658
Weighted Average Common Shares Outstanding, Basic (shares)	505.0	505.0	505.0	505.0
Effect of Stock Based Compensation Awards, Basic (shares)	0.0	0.0	0.0	0.0
Total Shares, Basic (shares)	505.0	505.0	505.0	505.0
Net Income, Basic (dollars per share)	$ 0.22	$ 0.37	$ 0.44	$ 1.30
Weighted Average Common Shares Outstanding, Diluted (shares)	505.0	505.0	505.0	505.0
Effect of Stock Based Compensation Awards, Diluted (shares)	2.0	3.0	2.0	3.0
Total Shares, Diluted (shares)	507.0	508.0	507.0	508.0
Net Income, Diluted (dollars per share)	$ 0.22	$ 0.37	$ 0.44	$ 1.30