Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Assets and Liabilities Measured at fair value on a recurring basis
Cash and cash equivalents	$ 15.5	$ 13.1
Restricted cash	1.4	3.8	$ 2.9
Short-term investments	0.2	0.2
Foreign currency hedges	7.9	1.3
Foreign currency hedges	1.6	7.1
Fair Value, Measurements, Recurring [Member]
Assets and Liabilities Measured at fair value on a recurring basis
Cash and cash equivalents	129.7	108.5
Restricted cash	1.4	3.8
Short-term investments	12.9	16.2
Foreign currency hedges	7.9	1.3
Total Assets	167.6	143.1
Foreign currency hedges	1.6	7.1
Total Liabilities	1.6	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	126.0	107.3
Restricted cash	1.4	3.8
Short-term investments	0.0	0.0
Foreign currency hedges	0.0	0.0
Total Assets	127.4	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	3.7	1.2
Restricted cash	0.0	0.0
Short-term investments	12.9	16.2
Foreign currency hedges	7.9	1.3
Total Assets	24.5	18.7
Foreign currency hedges	1.6	7.1
Total Liabilities	1.6	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