Derivative Instruments - Net Investment Hedges in Statements of Operations and Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative [Line Items]
Gains (losses) on foreign exchange forward contracts - cumulative translation adjustments, net of tax benefit	$ (14.9)	$ (9.1)	$ (15.5)	$ (27.3)
Forward exchange forward contracts
Derivative [Line Items]
Gains (losses) on foreign exchange forward contracts - other income, net	0.2		0.3
Gains (losses) on foreign exchange forward contracts - cumulative translation adjustments, net of tax benefit	1.5		1.3
Gains (losses) on foreign exchange forward contracts - cumulative translation adjustments, tax liability	$ 0.5		$ 0.4

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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Amount of tax expense (benefit), after reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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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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