Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 8,030	$ 7,817	$ 8,021	$ 7,799	$ 7,498	$ 8,179	$ 8,061	$ 8,647	$ 31,667	[1]	$ 32,385	[1]
Cost of Revenue	3,858	3,337	3,495	3,326	3,375	3,707	3,415	3,805	14,016	[2]	14,302	[2]
Gross profit	4,172	4,480	4,526	4,473	4,123	4,472	4,646	4,842	17,651		18,083
Product development	2,551	2,280	2,255	2,227	2,119	1,963	1,985	2,193	9,313	[2]	8,260	[2]
Sales and marketing	1,368	1,239	1,463	1,462	1,638	1,570	1,679	1,302	5,532	[2]	6,189	[2]
General and administrative	1,450	1,656	1,929	1,924	1,782	2,087	2,197	2,011	6,959	[2]	8,077	[2]
Restructuring charges	0	0	0	0	286	0	0	0	0		286
Total operating expenses	5,369	5,175	5,647	5,613	5,825	5,620	5,861	5,506	21,804		22,812
Loss from operations	(1,197)	(695)	(1,121)	(1,140)	(1,702)	(1,148)	(1,215)	(664)	(4,153)		(4,729)
Interest and other income (expense), net	(58)	(155)	(220)	(65)	567	(57)	503	(205)	(498)		808
Loss from operations before provision for income taxes	(1,255)	(850)	(1,341)	(1,205)	(1,135)	(1,205)	(712)	(869)	(4,651)		(3,921)
Income tax expense (benefit)	(53)	2	29	(6)	102	23	51	6	(28)		182
Net loss	$ (1,202)	$ (852)	$ (1,370)	$ (1,199)	$ (1,237)	$ (1,228)	$ (763)	$ (875)	$ (4,623)		$ (4,103)
Basic and diluted net loss per share from continuing operations attributable to Echelon Corporation Stockholders	$ (0.27)	$ (0.19)	$ (0.31)	$ (0.27)	$ (0.28)	$ (0.28)	$ (0.17)	$ (0.20)
Weighted Average Number of Shares Outstanding, Basic	4,520	4,460	4,445	4,434	4,432	4,431	4,420	4,417	4,465		4,425
Weighted Average Number of Shares Outstanding, Diluted	4,520	4,460	4,445	4,434	4,432	4,431	4,420	4,417	4,465		4,425

[1] Includes related party amounts of $0 and $1,313 in 2017 and 2016, respectively. See Note 13 for additional information on related party transactions.

[2] See Note 7 for summary of amounts included representing stock-based compensation expense.