3. Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Allowance for Credit Loss [Abstract]
Balance, beginning of year	$ 50	$ 50
Provision for doubtful accounts	0	0
Uncollectible accounts written off	0	0
Balance, end of year	$ 50	$ 50