Retirement Plans - Components of Net Periodic Pension (Credit) Cost (Details) - United States - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 0.6	$ 0.6	$ 1.1	$ 1.2
Expected return on plan assets	(0.8)	(0.8)	(1.6)	(1.6)
Amortization of net actuarial loss	0.1	0.1	0.2	0.2
Net periodic pension credit	(0.1)	(0.1)	(0.3)	(0.2)
Settlement loss	0.0	0.0	0.0	0.0
Total pension (credit) cost	$ (0.1)	$ (0.1)	$ (0.3)	$ (0.2)