Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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Nominal or face amount used to calculate payments on the derivative asset.

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Fair value, after the effects of master netting arrangements, of a 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. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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

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

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Amount, before tax and reclassification, of gain (loss) from derivative designated and qualifying as net investment hedge.

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Amount before tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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Amount, after tax, of reclassification from accumulated other comprehensive income (AOCI) of gain (loss) from increase (decrease) in fair value of net investment hedge.

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Derivative Financial Instruments and Credit Risk - Narrative (Details) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Derivative [Line Items]
Derivative, fair value		$ 2.0	$ 5.5
Interest Rate Swap
Derivative [Line Items]
Number of interest rate derivatives held		3
Not Designated as Hedging Instrument \| Foreign Exchange Contract
Derivative [Line Items]
Derivative, Term of Contract	2 years
Derivative asset, notional amount		$ 509.2
Cash Flow Hedging \| Designated as Hedging Instrument
Derivative [Line Items]
Derivative, effective portion recognized in other comprehensive income (loss)		1.8
Cash Flow Hedging \| Designated as Hedging Instrument \| Interest Rate Swap
Derivative [Line Items]
Derivative, fair value		2.7
Net Investment Hedging \| Designated as Hedging Instrument \| Interest Rate Swap
Derivative [Line Items]
Cross currency swap agreement		116.4
Net investment hedges		1.0
Other Assets \| Net Investment Hedging \| Designated as Hedging Instrument \| Interest Rate Swap
Derivative [Line Items]
Net investment hedges		1.4
Interest Expense \| Net Investment Hedging \| Designated as Hedging Instrument \| Interest Rate Swap
Derivative [Line Items]
Gains recorded under cross currency agreement		$ 1.3