Share-based compensation (Rollforward Of Company's Stock Options) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Options, Weighted-Average Fair Value and Total Intrinsic Value [Abstract]
Weighted-average fair value of stock options granted (US$ per share)	$ 19.89	$ 18.76	$ 29.71
Total intrinsic value of options exercised	$ 76	$ 122	$ 71
Total intrinsic value of options outstanding	331
Total intrinsic value of options exercisable	$ 293
Number of Options [Roll Forward]
Number of option outstanding, beginning of period	10,885,257	11,007,722	10,433,316
Number of options granted	1,958,279	2,073,940	1,842,690
Number of options exercised	(1,158,633)	(1,944,604)	(1,065,384)
Number of options forfeited	(206,720)	(251,801)	(202,900)
Number of option outstanding, end of period	11,478,183	10,885,257	11,007,722
Number of options exercisable	7,792,343
Weighted-Average Exercise Price [Roll Forward]
Weighted-average exercise price of options outstanding, beginning of period (US$ oer share)	$ 116.79	$ 108.25	$ 99.20
Weighted-average exercise price of options granted (US$ per share)	150.10	133.90	143.07
Weighted-average exercise price of options exercised (US$ per share)	86.90	84.13	73.57
Weighted average exercise price of options forfeited (US$ per share)	138.77	136.87	133.92
Weighted-average exercise price of options outstanding, end of period (US$ oer share	125.09	$ 116.79	$ 108.25
Weighted average exercise price of options exercisable (US$ per share)	$ 116.35

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Net number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Number of share options (or share units) exercised during the current period.

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