SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 24	$ 8	$ 23
Additions Charged to Cost and Expenses	1	16	0
Deductions	0	0	(15)
Balance at End of Year	25	24	8
Deferred tax asset valuation allowance
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	39,320	38,839	34,889
Additions Charged to Cost and Expenses	6,695	481	3,950
Deductions	0	0	0
Balance at End of Year	$ 46,015	$ 39,320	$ 38,839