Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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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 number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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Stock-based Compensation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Restricted Stock Units
No. of Stock Units
Nonvested restricted stock units, beginning of period			782
Granted (in units)			204
Vested (in units)			(271)
Forfeited (in units)			(30)
Nonvested restricted stock units, end of period	685		685
Weighted Average Grant Date Fair Value
Nonvested restricted stock units, beginning of period			$ 19.84
Granted (in dollars per share)			37.37
Vested (in dollars per share)			19.35
Forfeited (in dollars per share)			22.90
Nonvested restricted stock units, end of period	$ 25.13		$ 25.13
Stock-based Compensation
Unrecognized compensation cost	$ 12.5		$ 12.5
Weighted average period over which unrecognized compensation cost is expected to be recognized			2 years 1 month 6 days
Selling, General and Administrative Expenses
Stock-based Compensation
Share-based compensation costs recognized	$ 1.7	$ 1.3	$ 5.3	$ 3.4