Earnings Per Share (EPS) And Dividends (Basic And Diluted Earnings Per Share Computation) (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share, Diluted [Line Items]
Net Income									$ 1,518	$ 1,243	$ 1,275
Effect of Stock Based Compensation Awards, Basic									0	0	0
Total Shares, Basic	506	506	506	506	506	506	506	507	506	506	506
Effect of Stock Based Compensation Awards, Diluted									2	2	1
Total Shares, Diluted	508	507	508	508	508	508	508	507	508	508	507
Weighted Average Common Shares Outstanding Before Various Effects Basic									506	506	506
Weighted Average Common Shares Outstanding Before Various Effects Diluted									506	506	506
Earnings Per Share, Basic	$ 0.94	$ 0.88	$ 0.42	$ 0.76	$ 0.40	$ 0.77	$ 0.66	$ 0.63	$ 3.00	$ 2.46	$ 2.52
Earnings Per Share, Diluted	$ 0.94	$ 0.87	$ 0.42	$ 0.76	$ 0.39	$ 0.77	$ 0.66	$ 0.63	$ 2.99	$ 2.45	$ 2.51
Stock Options Excluded from Weighted Average Common Shares used for diluted EPS									0.4	1.6	1.8