Fair value, after offset of derivative asset, of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be and before offset against a right to receive collateral under a master netting arrangement. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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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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Nominal or face amount used to calculate payment on derivative.

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- Definition

Period remaining until the derivative contract matures, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a rate subject to change from time to time.

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Number of interest rate derivative instruments held by the entity at the reporting date.

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Represents the amount of benefit recorded to net finance costs related expired derivative contracts.

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Derivative Instruments - Interest rate swap agreement (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) agreement	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) agreement	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) agreement	Dec. 31, 2016 agreement
Interest rate contract
Derivative [Line Items]
Borrowings at variable interest rates	$ 559.7		$ 559.7		$ 404.3
Number of interest rate swap agreements \| agreement	2		2		1	1
Derivative, notional amount	$ 100.0		$ 100.0		$ 100.0
Net fair value of swap liability	5.4		5.4		$ 1.7
Gain (loss) recorded to net finance costs	$ (0.6)	$ 0.2	$ (0.6)	$ 0.4
2016 swap agreement
Derivative [Line Items]
Remaining maturity term			10 months
2019 swap agreement
Derivative [Line Items]
Remaining maturity term			48 months