Restructuring - Narrative (Details)	3 Months Ended								9 Months Ended	12 Months Ended
	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($) employee	Mar. 31, 2017 USD ($) employee	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Restructuring Cost and Reserve [Line Items]
Net loss from continuing operations	$ (1,858,000)	$ (1,773,000)	$ (3,114,000)	$ (4,522,000)	$ (7,805,000)	$ (3,177,000)	$ (3,916,000)	$ (1,977,000)		$ (11,267,000)	$ (16,875,000)	$ 9,471,000
Net (loss) income	(1,858,000)	(1,773,000)	$ (3,114,000)	$ (4,522,000)	(7,805,000)	$ (3,177,000)	$ (3,916,000)	$ (1,989,000)		(11,267,000)	(16,887,000)	8,780,000
Net cash (used in) provided by continuing operations										(5,868,000)	(17,999,000)	28,161,000
Net (decrease) increase in cash and cash equivalents										(5,868,000)	(18,011,000)	27,205,000
Cash and cash equivalents	10,761,000				$ 16,629,000					10,761,000	16,629,000	34,640,000	$ 7,435,000
Decrease in operating expense										(8,400,000)
Restructuring costs and asset impairment charges										1,800,000
Loss on impairment										185,000	857,000	0
Debt and capital lease obligations		$ 0							$ 0
Number of positions eliminated | employee			17	20
Restructuring										1,662,000	$ 0	$ 0
Obligations to be satisfied, term									12 months
Estimate of sublease payments to be received										1,200,000
Operating lease, liability	$ 1,700,000									1,700,000
Severance and Related Benefits
Restructuring Cost and Reserve [Line Items]
Restructuring										770,000
Facilities
Restructuring Cost and Reserve [Line Items]
Restructuring										708,000
Other
Restructuring Cost and Reserve [Line Items]
Restructuring										$ 186,000