Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2019
Property and equipment, gross	$ 885	$ 817
Less: accumulated depreciation	794	765
Property and equipment, net	$ 91	52	$ 97
Minimum [Member]
Property and equipment, Life	3 years
Maximum [Member]
Property and equipment, Life	7 years
Manufacturing Equipment [Member]
Property and equipment, gross	$ 768	$ 700
Manufacturing Equipment [Member] \| Minimum [Member]
Property and equipment, Life	3 years	3 years
Manufacturing Equipment [Member] \| Maximum [Member]
Property and equipment, Life	7 years	7 years
Research Equipment [Member]
Property and equipment, gross	$ 37	$ 37
Property and equipment, Life	5 years	5 years
Computer Equipment [Member]
Property and equipment, gross	$ 43	$ 43
Computer Equipment [Member] \| Minimum [Member]
Property and equipment, Life	3 years	3 years
Computer Equipment [Member] \| Maximum [Member]
Property and equipment, Life	4 years	4 years
Furniture and Fixtures [Member]
Property and equipment, gross	$ 37	$ 37
Property and equipment, Life	7 years	7 years

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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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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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.

+ References

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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.

+ References

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