Significant Accounting Policies - Property, Plant and Equipment (Details)	12 Months Ended
	Dec. 31, 2018
Tooling and manufacturing equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	1 year
Tooling and manufacturing equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	3 years
Furniture and office equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	3 years
Purchased software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	3 years
Capitalized internally-developed software [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	2 years
Capitalized internally-developed software [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	8 years
Leasehold improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	10 years