Income Taxes - Uncertain Tax Positions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of the total amounts of uncertain tax positions
Balance at January 1,	$ 10.3	$ 12.9	$ 7.0
Increases in prior period tax positions	0.4	0.0	0.5
Decreases in prior period tax positions	(1.0)	(2.6)	0.0
Increases in current period tax positions	0.7	0.6	5.5
Decreases due to lapse of statute of limitations	(1.0)	(0.3)	0.0
Increases due to change in tax rates	0.4	0.0	0.0
Increases from foreign exchange rate changes	0.2
Decreases from foreign exchange rate changes		(0.3)	(0.1)
Balance at December 31,	10.0	10.3	$ 12.9
Benefit for uncertain tax positions, if recognized	9.6
Accrued for interest and penalties related to uncertain income tax positions	0.1	0.2
Deferred Tax Asset
Reconciliation of the total amounts of uncertain tax positions
Balance at January 1,	7.6
Balance at December 31,	2.3	7.6
Deferred Tax Liability
Reconciliation of the total amounts of uncertain tax positions
Balance at January 1,	1.2
Balance at December 31,	5.3	1.2
Other Noncurrent Liabilities
Reconciliation of the total amounts of uncertain tax positions
Balance at January 1,	1.5
Balance at December 31,	$ 2.4	$ 1.5