Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and Equipment, Gross	$ 398	$ 398
Accumulated depreciation and amortization	(379)	(374)
Property and equipment, net	$ 19	24
Computer Equipment
Property Plant And Equipment [Line Items]
Estimated Life	3 years
Property and Equipment, Gross	$ 65	65
Lab Equipment
Property Plant And Equipment [Line Items]
Estimated Life	5 years
Property and Equipment, Gross	$ 142	142
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Estimated Life	5 years
Property and Equipment, Gross	$ 62	62
Computer Software
Property Plant And Equipment [Line Items]
Estimated Life	3 years
Property and Equipment, Gross	$ 70	70
Leasehold Improvements
Property Plant And Equipment [Line Items]
Estimated Life	Lesser of useful life or life of the lease
Property and Equipment, Gross	$ 59	$ 59

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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Describes the periods of time over which an entity anticipates to receive utility from its property, plant and equipment (that is, the periods of time over which an entity allocates the initial cost of its property, plant and equipment).

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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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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