Other Financial Information - Narrative (Details)	3 Months Ended	9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)
Disaggregation of Revenue [Line Items]
Deferred commission	$ 26,900,000	$ 26,900,000
Amortization of deferred commission	31,200,000	109,400,000
Impairment loss	0	0
Product
Disaggregation of Revenue [Line Items]
Contract with customer, liability, revenue recognized	21,100,000	77,600,000
Service
Disaggregation of Revenue [Line Items]
Contract with customer, liability, revenue recognized	$ 150,000,000	$ 581,300,000