Schedule II. - VALUATION AND QUALIFYING ACCOUNTS (Details) - Allowance for doubtful accounts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Valuation and Qualifying Accounts
Balance at beginning of year	$ 245	$ 263	$ 375
Charged to cost and expenses	189	93	103
Deductions	(334)	(111)	(215)
Balance at end of year	$ 100	$ 245	$ 263