Restructuring - Narrative (Details) $ in Thousands	3 Months Ended									9 Months Ended	12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($) employee	Mar. 31, 2017 USD ($) employee	Dec. 31, 2016 USD ($)	Sep. 30, 2017	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Restructuring Cost and Reserve [Line Items]
Net loss	$ (3,000)	$ (1,920)	$ (1,801)	$ (2,390)	$ (1,858)	$ (1,773)	$ (3,114)	$ (4,522)			$ (9,111)	$ (11,267)	$ (16,887)
Net cash (used in) provided by continuing operations											(4,426)	(5,868)	(17,999)
Cash and cash equivalents	6,335				10,761				$ 16,629		6,335	10,761	16,629	$ 34,640
Number of positions eliminated | employee							17	20
Restructuring charges												1,786
Decrease in operating expense											3,600	8,400
Restructuring costs and asset impairment charges												1,800
Restructuring											111	1,662	0
Loss on impairment									$ 900		0	185	$ 857
Obligations to be satisfied, term										12 months
Estimate of sublease payments to be received											700
Operating lease, liability	1,100										1,100
Borrowings	2,219				$ 0						2,219	0
Severance and Related Benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges												770
Restructuring												800
Facilities
Restructuring Cost and Reserve [Line Items]
Restructuring charges												830
Restructuring											100	700
Other
Restructuring Cost and Reserve [Line Items]
Restructuring charges												186
Restructuring												$ 100
Revolving Credit Facility
Restructuring Cost and Reserve [Line Items]
Borrowings	$ 2,200										$ 2,200