New Accounting Pronouncements New Accounting Pronouncements (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other current assets	$ 2.2			$ 2.1
Other assets	7.0			6.9
Accumulated deficit	(1,028.9)			(1,027.5)
Deferred revenue	10.9			10.7
Deferred revenue, current	7.4
Deferred revenue, noncurrent	3.5
Contract with customer, revenue recognized	2.8
Selling, general and administrative	5.2	$ 8.9
Other income (expense), net	0.6	0.1
Support Contract Costs
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred contract costs	0.8			0.8
Deferred contract costs, current	0.5
Deferred contract costs, noncurrent	0.3
Deferred contract costs, amortization	0.2
Sales Commissions
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred contract costs	0.3			$ 0.3
Deferred contract costs, current	0.2
Deferred contract costs, noncurrent	$ 0.1
Capitalized contract cost, amortization period (up to)	5 years
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Support contract duration	1 year
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Support contract duration	5 years
Restatement Adjustment | Accounting Standards Update 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Selling, general and administrative	$ (0.2)	(0.1)
Other income (expense), net	(0.2)	(0.1)
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other current assets			$ 0.2
Other assets			0.1
Accumulated deficit			$ 0.3
Product revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contract with customer	6.5	7.2
Support contract revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contract with customer	$ 2.8	$ 2.4