Share-Based Compensation - Awards Granted (Details)	6 Months Ended
Jun. 30, 2018 USD ($) $ / shares shares
MSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares) \| shares	428,574
Weighted average fair value (in usd per share) \| $ / shares	$ 34.22
Expected volatility	32.62%
Risk-free rate	2.37%
Expected term (in years)	2 years 11 months 12 days
Expected dividends \| $	$ 0
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares) \| shares	103,819
Weighted average fair value (in usd per share) \| $ / shares	$ 34.21
Expected volatility	32.61%
Risk-free rate	2.37%
Expected term (in years)	2 years 11 months 12 days
Expected dividends \| $	$ 0
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares) \| shares	44,000
Weighted average fair value (in usd per share) \| $ / shares	$ 36.92

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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- Definition

The estimated amount of dividends to be paid to holders of the underlying shares (expected dividends) over the option's term. Dividends are taken into account because payment of dividends to shareholders reduces the fair value of the underlying shares, and option holders generally do not receive dividends.

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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

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

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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

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.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
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-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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