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								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share, Diluted [Line Items]
Net Income									$ 1,679	$ 1,518	$ 1,243
Effect of Stock Based Compensation Awards, Basic									0.0	0.0	0.0
Total Shares, Basic	505.0	505.0	506.0	506.0	506.0	506.0	506.0	506.0	505.0	506.0	506.0
Effect of Stock Based Compensation Awards, Diluted									3.0	2.0	2.0
Total Shares, Diluted	508.0	508.0	508.0	508.0	508.0	507.0	508.0	508.0	508.0	508.0	508.0
Weighted Average Common Shares Outstanding Before Various Effects Basic									505.0	506.0	506.0
Weighted Average Common Shares Outstanding Before Various Effects Diluted									505.0	506.0	506.0
Earnings Per Share, Basic	$ 0.61	$ 0.87	$ 0.68	$ 1.16	$ 0.94	$ 0.88	$ 0.42	$ 0.76	$ 3.32	$ 3.00	$ 2.46
Earnings Per Share, Diluted	$ 0.60	$ 0.87	$ 0.68	$ 1.15	$ 0.94	$ 0.87	$ 0.42	$ 0.76	$ 3.30	$ 2.99	$ 2.45
Stock Options Excluded from Weighted Average Common Shares used for diluted EPS									0.5	0.4	1.6