Stock-based compensation (Textual) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount by which the pool of available shares will be reduced for each stock option granted	1
The amount of common stock available under the plan for future grants and/or issuances (in shares)	28,000,000
Description of vesting of restricted stock units and stock options	RSUs and stock options generally vest in equal amounts on the second, third and fourth anniversaries of the grant date.
Total unrecognized compensation cost related to nonvested awards	$ 308
Weighted average number of years over which compensation cost related to nonvested awards is expected to be recognized	1 year 9 months 18 days
Period over which the grants of equity instruments vest	3 years
Number of common shares issued for each performance unit earned	1
RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
The number of shares by which the pool of available shares will be reduced for other types of awards granted	1.9
Number of shares added back for tax withholding on full value awards	1.9
Weighted average grant date fair value, granted (in usd per share)	$ 182.12	$ 179.18	$ 163.99
Total fair value of units that vested during the year	$ 160	$ 167	$ 182
Units outstanding (in shares)	3,100,000	3,100,000
Weighted-average grant date fair value	$ 174.97	$ 168.11
Units granted (in shares)	1,200,000
Units, forfeited (in shares)	200,000
Weighted average grant date fair value, forfeited (in usd per share)	$ 170.52
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period of stock options from date of grant	10 years
Total intrinsic value of stock options exercised during the year	$ 68	$ 53	60
Actual tax benefits realized from tax deductions from option exercises	$ 15	$ 12	$ 21
Performance units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
The number of shares by which the pool of available shares will be reduced for other types of awards granted	1.9
Number of shares added back for tax withholding on full value awards	1.9
Weighted average grant date fair value, granted (in usd per share)	$ 188.40	$ 189.21	$ 178.87
Total fair value of units that vested during the year	$ 176	$ 133	$ 219
Total unrecognized compensation cost related to nonvested awards	$ 113
Weighted average number of years over which compensation cost related to nonvested awards is expected to be recognized	1 year
Units outstanding (in shares)	2,000,000.0	2,000,000.0
Weighted-average grant date fair value	$ 185.64	$ 180.12
Units granted (in shares)	800,000
Units, forfeited (in shares)	200,000
Weighted average grant date fair value, forfeited (in usd per share)	$ 186.66

The amount of common stock available under the plan for future grants and/or issuances.

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Number of common shares issued for each performance unit earned.

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Number of Shares Added Back for Tax Withholding on Full Value Awards

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of tax benefit from exercise of option under share-based payment arrangement.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Description of service or performance condition required to be met for earning right to award under share-based payment arrangement. Includes, but is not limited to, combination of market, performance or service condition.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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