Schedule II - Valuation and Qualifying Accounts - Summary of 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 Beginning of Year	$ 1,061	$ 341	$ 304
Additions Charged/ (Credited) to Cost and Expenses	106	674	61
Additions Charged/ (Credited) to Other Accounts	150	69	(24)
Deductions	650	23
Balance End of Year	667	1,061	341
Valuation Allowance of Deferred Tax Assets [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance Beginning of Year	11,824	11,459	9,863
Additions Charged/ (Credited) to Cost and Expenses	476	315	1,673
Additions Charged/ (Credited) to Other Accounts	(37)	50	(77)
Balance End of Year	$ 12,263	$ 11,824	$ 11,459