Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for doubtful accounts and returns
Changes in Valuation and Qualifying Accounts
Balance at Beginning of Period			$ 77
Charged to Costs and Expenses	$ 818
Deductions		$ 0	77
Balance at End of Period	818
Deferred tax valuation allowance
Changes in Valuation and Qualifying Accounts
Balance at Beginning of Period	6,835	7,136	122,966
Charged to Costs and Expenses	1,492	(441)	(115,831)
Deductions		(140)	(1)
Balance at End of Period	$ 8,327	$ 6,835	$ 7,136