Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for doubtful accounts
Valuation and Qualifying Accounts
Balance at Beginning of Period	$ 49	$ 12	$ 6
Additions Charged to Costs and Expenses	(10)	43	12
Deductions		(6)	(6)
Balance at End of Period	39	49	12
Deferred tax asset valuation allowance
Valuation and Qualifying Accounts
Balance at Beginning of Period	4,489	4,626	4,672
Additions Charged to Costs and Expenses	2,900	(137)	376
Deductions			(422)
Balance at End of Period	$ 7,389	$ 4,489	$ 4,626