Share-Based Compensation - Summary of Stock Options (Details) - $ / shares shares in Thousands	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based awards, stock options, granted (in shares)	1,283	1,417
Share-based awards, stock options, weighted-average grant date fair value (in dollars per share)	$ 22.48	$ 18.73
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based awards, restricted stock units, granted (in shares)	525	603
Share-based awards, restricted stock units, weighted-average grant date fair values (in dollar per share)	$ 70.62	$ 57.65
Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based awards, restricted stock units, granted (in shares)	165	110
Share-based awards, restricted stock units, weighted-average grant date fair values (in dollar per share)	$ 75.39	$ 56.91

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).

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

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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

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

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

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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.

+ 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 (d)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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