Amount of shares earned as a % of target award.

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Award percentage attained

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Award percentage earned based on metric over the performance period.

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No definition available.

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- Definition

Number of performance metrics in restricted shares award type plan.

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No definition available.

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Number of shares issued pursuant to the terms of a deferred compensation arrangement.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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-Publisher FASB
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- Definition

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

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

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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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-Paragraph 2
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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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-Name Accounting Standards Codification
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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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Equity Awards - Restricted Stock Units Narrative (Details) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018 USD ($) number	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) number Rate shares	Jun. 30, 2017 USD ($)	Dec. 31, 2017
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares issued related to director fee deferrals			4,509
Number of Unvested Restricted Stock Units Granted			306,075
Unrecognized unvested restricted shares-based compensation expense \| $	$ 10.6		$ 10.6
Weighted-average period for recognition of the unrecognized unvested restricted shares-based compensation expense			2 years 5 months
Plan 1 [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Unvested Restricted Stock Units Granted			140,183
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period			3 years
Plan 5 [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period			1 year
Plan 5 [Member] \| Restricted Stock Units [Member] \| Non-employee independent director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Unvested Restricted Stock Units Granted			25,830
Plan 8 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of performance metrics in restricted shares award type plan \| number	2		2
Plan 8 [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Unvested Restricted Stock Units Granted			104,532
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period			3 years
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate			2.67%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate \| Rate			30.20%
3 year EPS CAGR metric [Member] \| Minimum [Member] \| Plan 8 [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Amount of shares earned % of target award			40.00%
3 year EPS CAGR metric [Member] \| Maximum [Member] \| Plan 8 [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award percentage earned based on metric over the performance period			50.00%
Share-based Compensation Arrangement by Share-based Payment Award, Amount of shares earned % of target award			200.00%
Total shareholder return metric [Member] \| Plan 3 [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Unvested Restricted Stock Units Granted			31,021
Share-based Compensation Arrangement by Share-based Payment Award, Award percentage attained					126.90%
Total shareholder return metric [Member] \| Minimum [Member] \| Plan 3 [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Amount of shares earned % of target award			0.00%
Total shareholder return metric [Member] \| Minimum [Member] \| Plan 8 [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Amount of shares earned % of target award			0.00%
Total shareholder return metric [Member] \| Maximum [Member] \| Plan 3 [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Amount of shares earned % of target award			200.00%
Total shareholder return metric [Member] \| Maximum [Member] \| Plan 8 [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award percentage earned based on metric over the performance period			50.00%
Share-based Compensation Arrangement by Share-based Payment Award, Amount of shares earned % of target award			200.00%
Selling, General and Administrative Expenses [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares-based compensation expense \| $	$ 1.3	$ 1.7	$ 2.5	$ 3.0