Retirement Plans - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) payment_option	Dec. 31, 2016 USD ($)	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]
Pension expense	$ 0.8	$ 2.6
Employer contributions in current fiscal year	0.5
Estimated future employer contributions in next fiscal year	2.8
Estimated amortization of net actuarial loss amount	0.8
Estimated amortization of net prior service credit	0.0
Estimated amortization of net obligation at transition	0.0
United States
Defined Benefit Plan Disclosure [Line Items]
Employer contributions in current fiscal year	$ 0.4	0.1
Minimum service years to be entitled to pension benefits	3 years
Pay credits as a percentage of each participant's eligible earnings			0.03	0.06
Interest credit rate in current year	2.86%
Interest credit rate in next fiscal year	2.80%
Pension settlement loss	$ 1.1	2.9
Number of payment options | payment_option	4
Total pension cost	$ 0.6	2.4
United States | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations	65.00%
United States | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations	25.00%
United States | Other investments
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations	10.00%
Germany
Defined Benefit Plan Disclosure [Line Items]
Employer contributions in current fiscal year	$ 0.1	(2.7)
Total pension cost	$ 0.2	$ 0.2