Fair Value Measurements (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Fair value of assets and liabilities measured on recurring basis
Accumulated other comprehensive gain (loss) associated with foreign exchange rate forward contracts	$ 0.4	$ (0.1)
Recurring basis
Fair value of assets and liabilities measured on recurring basis
Short-term investments	12.4	34.6
Forward contracts	2.4	2.3
Total	14.8	36.9
Recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair value of assets and liabilities measured on recurring basis
Short-term investments	12.4	34.6
Total	12.4	34.6
Recurring basis \| Significant Observable Inputs (Level 2)
Fair value of assets and liabilities measured on recurring basis
Forward contracts	2.4	2.3
Total	$ 2.4	$ 2.3

Amount after tax, before 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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