Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year		$ 456	$ 309	$ 249
Charged to costs and expenses			159	163
Deductions/ net charge-offs	[1]	(161)	(12)	(103)
Balance at end of year		295	456	309
Valuation Allowance for Deferred Income Taxes [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year		2,465	1,553	1,582
Charged to costs and expenses			912
Deductions/ net charge-offs	[1]	(167)		(29)
Balance at end of year		$ 2,298	$ 2,465	$ 1,553

[1] Credits to the allowance for doubtful accounts represent the write-off of bad debts net of recoveries. Credits to the valuation allowance for deferred income taxes represent adjustments to existing valuation allowances.