Schedule II - Valuation and Qualifying Accounts (Details) - Accounts receivable allowance [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 179	$ 465	$ 541
Charged/(Credited) to Costs and Expenses, Additions and Deductions	(21)	(194)	34
Charged to Other Accounts, Additions and Deductions	0	0	0
Uncollectible Accounts Written-off	10	92	110
Balance at End of Period	$ 148	$ 179	$ 465