Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Stock-based compensation awards
Share-based Compensation Arrangement by Share-based Payment Award Long Service Separation Eligibility Required Minimum Age	55 years
Share-based Compensation Arrangement by Share-based Payment Award Long Service Separation Eligibility Minimum Term of Service	5 years
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Minimum			25.10%	21.50%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Maximum			38.70%	33.00%
Stock-based compensation expense, before tax (in dollars)	$ 57	$ 52	$ 170	$ 164
Assumptions used in determining the fair value of the stock-based awards
Weighted-average dividend yield (as a percent)			2.56%	2.70%
Weighted-average volatility (as a percent)			29.10%	30.20%
Risk-free interest rates, low end of range (as a percent)			2.48%	2.02%
Risk-free interest rates, high end of range (as a percent)			2.68%	2.87%
Weighted-average expected lives (in years)			7 years	8 years
Unrecognized compensation cost related to nonvested stock-based compensation awards (in dollars)	$ 201		$ 201
Term of amortization of unrecognized compensation cost over weighted-average remaining requisite service periods (in years)			1 year 7 months 6 days
Stock Options
Stock-based compensation awards
Shares Granted (in shares)			1,499,524	1,605,220
Weighted-Average Fair Value Per Share (in dollars per share)			$ 40.98	$ 46.11
Weighted-Average Grant Date Stock Price (in dollars per share)	$ 138.35	$ 150.90	138.35	150.90
RSUs
Stock-based compensation awards
Weighted-Average Grant Date Stock Price (in dollars per share)	138.35	150.64	$ 138.35	$ 150.64
Shares Granted (in shares)			657,389	722,521
Weighted-Average Fair Value Per Share (in dollars per share)			$ 138.35	$ 150.64
PRSUs
Stock-based compensation awards
Weighted-Average Grant Date Stock Price (in dollars per share)	$ 138.35	$ 150.93	$ 138.35	$ 150.93
Shares Granted (in shares)			342,097	344,866
Weighted-Average Fair Value Per Share (in dollars per share)			$ 138.35	$ 150.93

The stock price per share on the grant date for issuance to employees under the plan.

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- Definition

Represents the minimum term of service to meet the criteria for a Long Service Separation.

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Represents the required minimum age of a participant upon separation from service to meet the criteria for a Long Service Separation.

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- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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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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- Definition

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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- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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- Definition

The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The estimated measure of the minimum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

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The minimum risk-free interest rate assumption that is used in valuing an option on its own shares.

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Rate of weighted-average expected volatility for award under share-based payment arrangement.

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- Definition

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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- Definition

Net number of non-option equity instruments granted to participants.

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Gross 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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Expected term of 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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