CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Preferred Stock [Member] Convertible Preferred Stock Series B [Member]	Preferred Stock [Member] Convertible Preferred Stock Series C [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income [Member]	Total	Convertible Preferred Stock Series C [Member]
Beginning balance at Dec. 31, 2016	$ 1	$ 0	$ 2	$ 197,475	$ (182,443)	$ 2	$ 15,037
Beginning balance (in shares) at Dec. 31, 2016	6,000	0	2,166,898
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss							(3,974)
Ending balance at Mar. 31, 2017							11,171
Beginning balance at Dec. 31, 2016	$ 1	$ 0	$ 2	197,475	(182,443)	2	15,037
Beginning balance (in shares) at Dec. 31, 2016	6,000	0	2,166,898
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss							(1,515)
Ending balance at Jun. 30, 2017							13,857
Beginning balance at Dec. 31, 2016	$ 1	$ 0	$ 2	197,475	(182,443)	2	15,037
Beginning balance (in shares) at Dec. 31, 2016	6,000	0	2,166,898
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss							(20,592)
Ending balance at Sep. 30, 2017							20,754
Beginning balance at Dec. 31, 2016	$ 1	$ 0	$ 2	197,475	(182,443)	2	15,037
Beginning balance (in shares) at Dec. 31, 2016	6,000	0	2,166,898
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	$ 0	$ 0	$ 0	186	0	0	186
Issuance of convertible preferred stock in exchange for convertible debentures	$ 0	$ 4	$ 0	25,906	0	0	25,910
Issuance of convertible preferred stock in exchange for convertible debentures (in shares)	0	40,482	0
Conversion of convertible preferred stock into common stock	$ (1)	$ 0	$ 2	0	0	0	1
Conversion of convertible preferred stock into common stock (in shares)	(6,000)	(4,300)	2,066,182
Conversion of senior secured convertible debentures into common stock	$ 0	$ 0	$ 0	262	0	0	262
Conversion of senior secured convertible debentures into common stock (in shares)	0	0	70,000
Issuance of common stock for fractional shares in reverse stock split (in shares)			1,345
Other comprehensive income loss			$ 0	0	0	(2)	(2)
Net loss			(8,851)	0	(21,514)	0	(21,514)	$ (12,663)
Ending balance at Dec. 31, 2017	$ 0	$ 4	$ 4	223,829	(203,957)	0	19,880
Ending balance (in shares) at Dec. 31, 2017	0	36,182	4,304,425
Beginning balance at Mar. 31, 2017							11,171
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss							2,459
Ending balance at Jun. 30, 2017							13,857
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss							(19,077)
Ending balance at Sep. 30, 2017							20,754
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative accounting adjustment from adoption of new standard, net of tax | ASU 2014-09 [Member]			$ 0	0	(234)	0	(234)
Cumulative accounting adjustment from adoption of new standard, net of tax | ASU 2017-11 [Member]			0	2,614	(2,547)	0	67
Beginning balance at Dec. 31, 2017	$ 0	$ 4	4	223,829	(203,957)	0	19,880
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss							(2,042)
Ending balance at Mar. 31, 2018							17,623
Beginning balance at Dec. 31, 2017	$ 0	$ 4	$ 4	223,829	(203,957)	0	19,880
Beginning balance (in shares) at Dec. 31, 2017	0	36,182	4,304,425
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss							(3,910)
Ending balance at Jun. 30, 2018							30,603
Beginning balance at Dec. 31, 2017	$ 0	$ 4	$ 4	223,829	(203,957)	0	19,880
Beginning balance (in shares) at Dec. 31, 2017	0	36,182	4,304,425
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss							(5,492)
Ending balance at Sep. 30, 2018							29,388
Beginning balance at Dec. 31, 2017	$ 0	$ 4	$ 4	223,829	(203,957)	0	19,880
Beginning balance (in shares) at Dec. 31, 2017	0	36,182	4,304,425
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	$ 0	$ 0	$ 0	904	0	0	904
Conversion of convertible preferred stock into common stock	$ 0	$ (3)	$ 10	(7)	0	0	0
Conversion of convertible preferred stock into common stock (in shares)	0	(26,214)	9,744,916
Sale of common stock, net of offering costs	$ 0	$ 0	$ 16	14,648	0	0	14,664
Sale of common stock, net of offering costs (in shares)	0	0	15,893,745
Net loss			$ (2,909)	0	(4,033)	0	(4,033)	$ (1,124)
Ending balance at Dec. 31, 2018	$ 0	$ 1	$ 30	$ 241,988	$ (210,771)	$ 0	31,248
Ending balance (in shares) at Dec. 31, 2018	0	9,968	29,943,086
Beginning balance at Mar. 31, 2018							17,623
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss							(1,868)
Ending balance at Jun. 30, 2018							30,603
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss							(1,582)
Ending balance at Sep. 30, 2018							$ 29,388