Schedule II - Valuation and Qualifying Accounts Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts:
The roll forward of valuation accounts were as follows:
Balance at beginning of period	$ 454	$ 543	$ 733
Charged to costs and expenses	499	361	353
Deductions	(477)	(450)	(543)
Balance at end of period	476	454	543
Valuation allowance for deferred tax assets:
The roll forward of valuation accounts were as follows:
Balance at beginning of period	35,416	36,516	36,675
Charged to costs and expenses	(32,860)	(1,100)	(159)
Deductions	0	0	0
Balance at end of period	$ 2,556	$ 35,416	$ 36,516