Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Assets and Liabilities Measured at fair value on a recurring basis
Cash and cash equivalents	$ 21.3	$ 13.1
Restricted cash	1.3	3.8	$ 3.3
Short-term investments	0.1	0.2
Foreign currency hedges	6.3	1.3
Foreign currency hedges	1.1	7.1
Fair Value, Measurements, Recurring [Member]
Assets and Liabilities Measured at fair value on a recurring basis
Cash and cash equivalents	132.4	108.5
Restricted cash	1.3	3.8
Short-term investments	16.5	16.2
Foreign currency hedges	6.3	1.3
Total Assets	177.9	143.1
Foreign currency hedges	1.1	7.1
Total Liabilities	1.1	7.1
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Assets and Liabilities Measured at fair value on a recurring basis
Cash and cash equivalents	130.9	107.3
Restricted cash	1.3	3.8
Short-term investments	2.1	0.0
Foreign currency hedges	0.0	0.0
Total Assets	134.3	111.1
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	1.5	1.2
Restricted cash	0.0	0.0
Short-term investments	14.4	16.2
Foreign currency hedges	6.3	1.3
Total Assets	22.2	18.7
Foreign currency hedges	1.1	7.1
Total Liabilities	1.1	7.1
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