Significant Market Segments And Customers (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Significant market segments
Accounts receivable	$ 4,171	$ 4,203
Sales | International sales
Significant market segments
Direct sales percentage of sales	9.00%	11.00%
Sales | DaVita | Customer concentration
Significant market segments
Direct sales percentage of sales	50.00%	49.00%
Sales | Baxter | Customer concentration
Significant market segments
Direct sales percentage of sales	25.00%	27.00%
Sales | Nipro Medical Corporation
Significant market segments
Direct sales percentage of sales	7.00%	9.00%
Accounts receivable | DaVita
Significant market segments
Accounts receivable	$ 1,100	$ 1,200
Accounts receivable | Baxter
Significant market segments
Accounts receivable	$ 1,600	$ 2,000