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Financial Statement Components - Narrative (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Property, Plant and Equipment [Line Items]      
Depreciation and amortization of property and equipment $ 7.8 $ 7.9 $ 6.9
Favorable impact to basic and diluted EPS related to change in estimated useful life (in USD per share) $ (0.16) $ (0.23) $ (0.52)
Previously reported      
Property, Plant and Equipment [Line Items]      
Useful life, in years 3 years    
Service life | Adjustments      
Property, Plant and Equipment [Line Items]      
Depreciation and amortization of property and equipment $ (1.6)    
Favorable impact to basic and diluted EPS related to change in estimated useful life (in USD per share) $ 0.03    
Minimum | Service life      
Property, Plant and Equipment [Line Items]      
Useful life, in years 3 years    
Maximum | Service life      
Property, Plant and Equipment [Line Items]      
Useful life, in years 5 years