Share-based compensation (Rollforward Of Company's Stock Options) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Number of Options [Roll Forward]
Number of option outstanding, beginning of period	9,623,986	9,496,856	9,449,659
Number of options granted	1,892,641	1,782,903	1,821,063
Number of options exercised	(1,457,580)	(1,511,948)	(1,658,671)
Number of options forfeited	(205,551)	(143,825)	(115,195)
Number of option outstanding, end of period	9,853,496	9,623,986	9,496,856
Number of options exercisable, December 31, 2015	6,424,800
Weighted-Average Exercise Price [Roll Forward]
Weighted-average exercise price of options outstanding, beginning of period (US$ oer share)	$ 69.06	$ 61.84	$ 55.03
Weighted-average exercise price of options granted (US$ per share)	114.78	96.77	85.41
Weighted-average exercise price of options exercised (US$ per share)	60.88	54.84	48.17
Weighted average exercise price of options forfeited (US$ per share)	100.25	84.52	72.50
Weighted-average exercise price of options outstanding, end of period (US$ oer share	78.40	69.06	61.84
Weighted average exercise price of options exercisable, December 31, 2015 (US$ per share)	64.45
Options, Weighted-Average Fair Value and Total Intrinsic Value [Abstract]
Weighted-average fair value of stock options granted (US$ per share)	$ 18.49	$ 18.00	$ 17.29
Total intrinsic value of options exercised	$ 72	$ 73	$ 70
Total intrinsic value of options outstanding	379
Total intrinsic value of options exercisable, December 31, 2015	$ 337