Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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Amount of gain (loss) on sale or disposal of property, plant and equipment assets, including oil and gas property and timber property.

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The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

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The cash inflow from the sale of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment at cost		$ 2,984	$ 3,375
Less: accumulated depreciation		(2,595)	(2,765)
Property and equipment, net		389	610
Depreciation		326	522	$ 681
Impairment loss on equipment and software			200
Gain on sale		$ (24)	(2)	$ (203)
Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life		2 years
Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life		15 years
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment at cost		$ 1,297	$ 1,511
Net proceeds	$ 200
Gain on sale	$ 15
Equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life		3 years	3 years
Equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life		15 years	15 years
Tooling
Property, Plant and Equipment [Line Items]
Property and equipment at cost		$ 203	$ 371
Tooling \| Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life		2 years	2 years
Tooling \| Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life		5 years	5 years
Vehicles
Property, Plant and Equipment [Line Items]
Property and equipment at cost		$ 47	$ 47
Property and equipment, useful life		5 years	5 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment at cost		$ 137	$ 137
Property and equipment, useful life		5 years	5 years
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment at cost		$ 1,028	$ 1,043
Property and equipment, useful life		3 years	3 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment at cost		$ 211	$ 211
Finance lease right-of-use asset
Property, Plant and Equipment [Line Items]
Property and equipment at cost		13
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment at cost		$ 48	$ 55