Stock Option Plans (Tables)

3 Months Ended

12 Months Ended

Mar. 31, 2020

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Schedule of stock option activity

The following table summarizes stock option activity and related information for the three months ended March 31, 2020 and 2019:

	Number of Shares Available for Grant	Number of Options Outstanding	Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Term (in Years)	Aggregate Intrinsic Value
Balance at January 1, 2020	1,550,628	2,473,130	$	4.67	6.84	$	—
Options authorized	1,029,588	—	$	—
Options exercised	—	(3,346)	$	3.76
Options canceled	11,693	(11,693)	$	4.37
Balance at March 31, 2020	2,591,909	2,458,091	$	4.74	6.58	$	—
Exercisable at March 31, 2020		2,160,101	$	4.86	6.44	$	—
Balance at January 1, 2019	1,648,039	2,377,180	$	4.83	7.46	$	—
Options canceled	5,635	(5,635)	$	5.29
Balance at March 31, 2019	1,653,674	2,371,545	$	4.85	7.23	$	—
Exercisable at March 31, 2019		1,834,360	$	5.00	7.09	$	—

The following table summarizes stock option activity under the 2007 Plan and 2015 Plan and related information:

	Number of Shares Available for Grant	Number of Options Outstanding	Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Term (in Years)	Aggregate Intrinsic Value
Balance at January 1, 2018	1,589,381	2,435,837	$	4.80	8.38	$	—
Options granted	(46,005)	46,005	$	4.34
Options canceled	104,662	(104,662)	$	4.70
Balance at December 31, 2018	1,648,038	2,377,180	$	4.79	7.46	$	—
Options granted	(209,908)	209,908	$	3.14
Options exercised	—	(1,392)	$	3.86
Options canceled	112,498	(112,498)	$	4.34
Balance at December 31, 2019	1,550,628	2,473,198	$	4.67	6.84	$	—
Exercisable at December 31, 2019		2,079,809	$	4.95	6.65	$	—

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

The assumptions used to value options granted to employees during the year ended December 31, 2019 and 2018, were as follows:

	Year Ended December 31,
	2019	2018
Weighted average expected life (in years)	5.46	5.84
Risk-free interest rate	1.34% - 1.94%	2.51% - 2.52%
Expected volatility	39.4% - 39.8%	38.1% - 38.2%
Weighted average grant date fair value	$1.04	$0.84
Dividend yield	—%	—%

Stock-based compensation expense

The accompanying condensed consolidated statement of operations and comprehensive loss includes stock-based compensation expense as follows (in thousands):

	Three Months Ended March 31,
	2020		2019
Cost of revenue	$	15	$	10
Research and development	46		43
Sales and marketing	7		9
General and administrative	64		77
Total	$	132	$	139

The accompanying consolidated statement of operations includes stock-based compensation expense as follows (in thousands):

	Year Ended December 31,
	2019		2018
Cost of revenue	$	60	$	41
Research and development	196		186
Sales and marketing	30		45
General and administrative	280		313
Total	$	566	$	585