Capital Stock (Narrative) (Details) - USD ($) $ / shares in Units, $ 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
Capital Stock [Line Items]
Cash dividends declared, per share of common stock	$ 0.38	$ 0.345	$ 0.345	$ 0.345	$ 0.345	$ 0.305	$ 0.305	$ 0.305	$ 1.415	$ 1.26	$ 1.10
Shares repurchased (in shares)									7,400,000	1,300,000	4,800,000
Repurchase and retirement of shares of common stock									$ 700	$ 100	$ 317
Remaining shares authorized to be repurchased	$ 1,883								$ 1,883
Capital shares reserved for future issuance	15,000,000				19,000,000				15,000,000	19,000,000
Preferred stock, capital shares reserved for future issuance	500,000								500,000
Preferred stock, par per share	$ 1								$ 1
Options granted for period in number of years									10 years
Aggregate intrinsic value of options exercised									$ 98	$ 113	$ 97
Options exercised during period, exercise price range, lower range limit									$ 38.71
Options exercised during period, exercise price range, upper range limit									$ 102.27
Compensation cost not yet recognized	$ 79								$ 79
Compensation cost not yet recognized, period for recognized									1 year 7 months
Restricted Stock Units (RSUs) [Member]
Capital Stock [Line Items]
Compensation cost not yet recognized	53								$ 53
Compensation cost not yet recognized, period for recognized									12 months
Weighted average grant date fair value, granted (in dollars per share)									$ 88.47	$ 76.61
Shares vested during the period									$ 43
Performance Stock Units (PSUs) [Member]
Capital Stock [Line Items]
Compensation cost not yet recognized	$ 18								$ 18
Compensation cost not yet recognized, period for recognized									1 year 3 months
Weighted average grant date fair value, granted (in dollars per share)									$ 92.96
Employee Stock Purchase Plans [Member]
Capital Stock [Line Items]
Percentage of closing stock price under ESPP									95.00%
Shares issued under the ESPP									157,931	150,167