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Derivative Financial Instruments - Fair Value of Derivatives Included in Balance Sheets (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Stockholders’ equity (deficit)
Accumulated other comprehensive loss (net of tax of $0.2 million)	$ 0.4	$ 0.0	$ 0.6	$ 0.0
Accumulated other comprehensive loss, tax			0.2
Cash Flow Hedging \| Foreign Currency Forward Contract \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Assets	0.0		0.0		$ 0.0
Liabilities	0.7		0.7		0.0
Stockholders’ equity (deficit)
Accumulated other comprehensive loss (net of tax of $0.2 million)			0.6		0.0
Cash Flow Hedging \| Foreign Currency Forward Contract \| Designated as Hedging Instrument \| Prepaid expenses and other current assets
Derivatives, Fair Value [Line Items]
Assets	0.0		0.0		0.0
Cash Flow Hedging \| Foreign Currency Forward Contract \| Designated as Hedging Instrument \| Other assets
Derivatives, Fair Value [Line Items]
Assets	0.0		0.0		0.0
Cash Flow Hedging \| Foreign Currency Forward Contract \| Designated as Hedging Instrument \| Other accrued expenses
Derivatives, Fair Value [Line Items]
Liabilities	0.7		0.7		0.0
Cash Flow Hedging \| Foreign Currency Forward Contract \| Designated as Hedging Instrument \| Other non-current liabilities
Derivatives, Fair Value [Line Items]
Liabilities	$ 0.0		$ 0.0		$ 0.0