3. Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Allowance For Doubtful Accounts Details
Balance, beginning of year	$ 50	$ 49
Provision for doubtful accounts	0	17
Uncollectible accounts written off	0	(16)
Balance, end of year	$ 50	$ 50