Accounts Receivable (Allowance) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for credit losses:
Balance, beginning of period	$ 353	$ 264	$ 119
Provision for credit losses on accounts receivable, net of adjustments	153	91	174
Accounts receivable written off, net of recoveries	0	(2)	(29)
Balance, end of period	$ 506	$ 353	$ 264