Supplemental Balance Sheet Information - Narrative (Details) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 15, 2018 purchaser	Dec. 31, 2017 USD ($)
Supplemental Balance Sheet Disclosures [Line Items]
Reserves and allowances		$ 0.4		$ 0.4
Accounts receivable sold	$ 1.2
Proceeds from sale of accounts receivable	$ 1.1
Repurchase of accounts receivable, term	5 months
Interest per month on receivables sold	2.00%
Income taxes receivable		2.2
Deferred revenue, current		7.1
Other Noncurrent Assets
Supplemental Balance Sheet Disclosures [Line Items]
Income taxes receivable		2.2
Equity securities		4.0
Other Current Liabilities
Supplemental Balance Sheet Disclosures [Line Items]
Deferred revenue, current		7.1		7.2
Levy accruals		5.4		5.6
Accrued payroll		1.1		1.5
Other Liabilities
Supplemental Balance Sheet Disclosures [Line Items]
Pension liabilities		23.3		$ 23.3
Sold Accounts Receivable Litigation | Obligation to Repurchase Receivables Sold
Supplemental Balance Sheet Disclosures [Line Items]
Number of accounts receivable purchasers with outstanding demands | purchaser			2
Loss contingency, damages sought		$ 0.5