Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance (in shares) at Dec. 31, 2018	13,968,852
Balance at Dec. 31, 2018	$ 14	$ 70,451	$ (24,010)	$ (69)	$ 46,386
Exercise of stock options (in shares)	79,420
Exercise of stock options		767			767
Issuance of common stock in settlement of restricted stock units, net of shares withheld for employee taxes (in shares)	97,746
Issuance of common stock in settlement of restricted stock units, net of shares withheld for employee taxes		(750)			(750)
Stock-based compensation expense		7,004			7,004
Net loss			(10,260)		(10,260)
Net change in unrealized gain (loss) on available-for-sale investments				10	10
Issuance of common stock for employee purchase plan (in shares)	53,803
Issuance of common stock for employee purchase plan		833			833
Balance (in shares) at Sep. 30, 2019	14,199,821
Balance at Sep. 30, 2019	$ 14	78,305	(34,270)	(59)	43,990
Balance (in shares) at Jun. 30, 2019	14,142,296
Balance at Jun. 30, 2019	$ 14	74,870	(31,642)	(60)	43,182
Exercise of stock options (in shares)	38,966
Exercise of stock options		437			437
Issuance of common stock in settlement of restricted stock units, net of shares withheld for employee taxes (in shares)	18,559
Issuance of common stock in settlement of restricted stock units, net of shares withheld for employee taxes		(180)			(180)
Stock-based compensation expense		3,178			3,178
Net loss			(2,628)		(2,628)
Net change in unrealized gain (loss) on available-for-sale investments				1	1
Balance (in shares) at Sep. 30, 2019	14,199,821
Balance at Sep. 30, 2019	$ 14	78,305	(34,270)	(59)	$ 43,990
Balance (in shares) at Dec. 31, 2019	14,315,586				14,315,586
Balance at Dec. 31, 2019	$ 14	82,346	(36,358)	(60)	$ 45,942
Exercise of stock options (in shares)	46,878				46,878
Exercise of stock options		419			$ 419
Issuance of common stock in settlement of restricted stock units, net of shares withheld for employee taxes (in shares)	481,387
Issuance of common stock in settlement of restricted stock units, net of shares withheld for employee taxes	$ 1	(3,341)			(3,340)
Stock-based compensation expense		8,057			8,057
Net loss			(26,065)		(26,065)
Net change in unrealized gain (loss) on available-for-sale investments				61	61
Issuance of common stock for employee purchase plan (in shares)	39,248
Issuance of common stock for employee purchase plan		437			437
Issuance of common stock in connection with public offering, net of offering costs of $2,303 (in shares)	2,742,750
Issuance of common stock in connection with public offering, net of offering costs of $2,303	$ 3	26,492			$ 26,495
Balance (in shares) at Sep. 30, 2020	17,625,849				17,625,849
Balance at Sep. 30, 2020	$ 18	114,410	(62,423)	1	$ 52,006
Balance (in shares) at Jun. 30, 2020	17,567,688
Balance at Jun. 30, 2020	$ 18	112,644	(60,166)	3	52,499
Exercise of stock options (in shares)	750
Exercise of stock options		8			8
Issuance of common stock in settlement of restricted stock units, net of shares withheld for employee taxes (in shares)	57,411
Issuance of common stock in settlement of restricted stock units, net of shares withheld for employee taxes		(224)			(224)
Stock-based compensation expense		1,982			1,982
Net loss			(2,257)		(2,257)
Net change in unrealized gain (loss) on available-for-sale investments				(2)	$ (2)
Balance (in shares) at Sep. 30, 2020	17,625,849				17,625,849
Balance at Sep. 30, 2020	$ 18	$ 114,410	$ (62,423)	$ 1	$ 52,006