Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Accounts receivable	$ 3.9	$ 2.9
Accrued expenses	6.7	4.6
Compensation	27.9	30.6
Deferred revenue	0.4	2.0
Net operating loss carryforwards	19.1	14.1
Fixed assets		0.8
Inventory	2.8	3.2
Foreign tax and other tax credit carryforwards	5.9	17.2
Unrealized currency gain/loss	3.2	3.0
Gross deferred tax assets	69.9	78.4
Less valuation allowance		(0.5)	$ (37.2)	$ (57.4)
Total deferred tax assets	69.9	77.9
Deferred tax liabilities:
Fixed assets	0.3
Foreign statutory reserves	0.9	1.1
Intangibles	13.0	7.2
Accrued expenses	0.6	1.2
Accrued Withholding Tax	16.1	2.0
Other	6.4
Total deferred tax liabilities	37.3	11.5
Net deferred tax assets	$ 32.6	$ 66.4