Amount of shares earned as a % of target award.

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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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- 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.

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

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

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

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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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Equity Awards - Restricted Stock Units Narrative (Details) - Restricted Stock Units [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares issued related to director fee deferrals			2,711
Number of Unvested Restricted Stock Units Granted			292,709
Unrecognized unvested restricted shares-based compensation expense	$ 12.3		$ 12.3
Weighted-average period for recognition of the unrecognized unvested restricted shares-based compensation expense			2 years 3 months 18 days
Plan 1 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Unvested Restricted Stock Units Granted			129,929
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period			3 years
Plan 5 [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] \| Non-employee independent director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Unvested Restricted Stock Units Granted			25,872
Plan 8 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Unvested Restricted Stock Units Granted			95,882
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			2.29%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate			26.70%
3 year EPS CAGR metric [Member] \| Maximum [Member] \| Plan 8 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award percentage earned based on metric over the performance period			50.00%
Total shareholder return metric [Member] \| Plan 3 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Unvested Restricted Stock Units Granted			38,315
Share-based Compensation Arrangement by Share-based Payment Award, Award percentage attained					139.00%
Total shareholder return metric [Member] \| Minimum [Member] \| Plan 3 [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]
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]
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]
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]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares-based compensation expense	$ 1.7	$ 1.3	$ 3.0	$ 2.5