New Accounting Pronouncements New Accounting Pronouncements (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other current assets	$ 2.2		$ 2.2			$ 2.1
Other assets	7.0		7.0			6.9
Accumulated deficit	(1,030.2)		(1,030.2)			(1,027.5)
Revenue from contact with customer	8.0	$ 8.8	17.4	$ 18.4
Deferred revenue	10.3		10.3			10.7
Deferred revenue, current	7.1		7.1
Deferred revenue, noncurrent	3.2		3.2
Contract with customer, revenue recognized	2.8		5.6
Selling, general and administrative	4.7	7.7	9.9	16.6
Other income (expense), net	(0.1)	(0.6)	0.5	(0.5)
Support Contract Costs
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred contract costs	0.7		0.7			0.8
Deferred contract costs, current	0.5		0.5
Deferred contract costs, noncurrent	0.2		0.2
Deferred contract costs, amortization	0.2		0.4
Sales Commissions
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred contract costs	0.3		0.3			$ 0.3
Deferred contract costs, current	0.2		0.2
Deferred contract costs, noncurrent	$ 0.1		$ 0.1
Capitalized contract cost, amortization period (up to)	5 years		5 years
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Support contract duration	1 year		1 year
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Support contract duration	5 years		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)	$ (0.4)	(0.2)
Other income (expense), net	(0.2)	(0.1)	(0.4)	(0.2)
Product revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contact with customer	5.4	6.4	11.8	13.6
Support contract revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contact with customer	$ 2.8	$ 2.5	$ 5.6	$ 4.9
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