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Summary of Significant Accounting Policies - Property and Equipment, Net Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Depreciation	$ 155,000	$ 425,000	$ 1,402,000
Goodwill impairment	0	0	0
Impairment charges	$ 0	$ 1,116,000	8,431,000
Computer equipment and software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	3 years
Furniture and fixtures [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	3 years
Furniture and fixtures [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	7 years
IPR&D [Member]
Property, Plant and Equipment [Line Items]
Impairment of IPR&D	$ 0		$ 0