Stock Plans (Details 1) - Employee Stock Purchase Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Maximum employee contribution to ESPP	$ 25
Maximum employee contribution to ESPP, percent of base compensation	10.00%
Common stock discount purchase price	95.00%
Shares available under employee stock purchase plan (in shares)	4,550,000
Shares purchased under ESPP (in shares)	10,041	8,834	8,006
Proceeds from stock plans	$ 393	$ 463	$ 457
Number of shares available under employee stock purchase plan (in shares)	250,790