Share-Based Payments Narrative (Details) shares in Millions	6 Months Ended
Jun. 30, 2018 $ / shares shares
Share-Based Payments
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross \| shares	0.9
Fair value of stock options, per share, estimated using a Black-Scholes option pricing model \| $ / shares	$ 41
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period	1 year
Share-Based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	6 years
Share-Based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	19.70%
Non-qualified stock options
Share-Based Payments
Share-Based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
Share-Based Compensation Arrangement By Share-based Payment Award Options Term	10 years
Restricted stock units
Share-Based Payments
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period \| shares	0.9
Share-Based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted-Average Grant-Date Fair Value \| $ / shares	$ 170
Performance stock units
Share-Based Payments
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period \| shares	0.1
Share-Based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted-Average Grant-Date Fair Value \| $ / shares	$ 226
Share-Based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years

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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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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- Definition

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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- 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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+ Details

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- Definition

The estimated measure of the 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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- 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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No definition available.

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- Definition

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

+ References

No definition available.

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- Definition

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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- Definition

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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- Definition

Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

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