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, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount				0
Net Income (Loss)	$ 269	$ 109	$ 827	$ 223
Weighted Average Common Shares Outstanding, Basic (shares)	504	505	504	505
Effect of Stock Based Compensation Awards, Basic (shares)	0	0	0	0
Total Shares, Basic (shares)	504	505	504	505
Net Income, Basic (dollars per share)	$ 0.53	$ 0.22	$ 1.64	$ 0.44
Weighted Average Common Shares Outstanding, Diluted (shares)	504	505	504	505
Effect of Stock Based Compensation Awards, Diluted (shares)	3	2	3	2
Total Shares, Diluted (shares)	507	507	507	507
Net Income, Diluted (dollars per share)	$ 0.53	$ 0.22	$ 1.63	$ 0.44