Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Assets and Liabilities Measured at fair value on a recurring basis
Cash and cash equivalents	$ 37.1	$ 26.6
Restricted cash	0.6	0.6
Short-term investments	0.8
Fair Value, Measurements, Recurring [Member]
Assets and Liabilities Measured at fair value on a recurring basis
Cash and cash equivalents	129.7	105.9
Restricted cash	0.6	0.6
Short-term investments	20.8	21.8
Foreign currency hedges	4.8	4.6
Total Assets	193.8	159.5
Foreign currency hedges	0.7	0.7
Total Liabilities	0.7	0.7
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Assets and Liabilities Measured at fair value on a recurring basis
Cash and cash equivalents	128.6	104.4
Restricted cash	0.6	0.6
Short-term investments	0.0	0.0
Foreign currency hedges	0.0	0.0
Total Assets	129.2	105.0
Foreign currency hedges	0.0	0.0
Total Liabilities	0.0	0.0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Assets and Liabilities Measured at fair value on a recurring basis
Cash and cash equivalents	1.1	1.5
Restricted cash	0.0	0.0
Short-term investments	20.8	21.8
Foreign currency hedges	4.8	4.6
Total Assets	26.7	27.9
Foreign currency hedges	0.7	0.7
Total Liabilities	0.7	0.7
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Assets and Liabilities Measured at fair value on a recurring basis
Cash and cash equivalents	0.0	0.0
Restricted cash	0.0	0.0
Short-term investments	0.0	0.0
Foreign currency hedges	0.0	0.0
Total Assets	0.0	0.0
Foreign currency hedges	0.0	0.0
Total Liabilities	$ 0.0	$ 0.0