SCHEDULE II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 12,682	$ 12,892
Charged to Costs and Expenses	0	0
Transferred to Other Accounts	0	(210)
Collected/ Recovered	0	0
Balance at End of Year	$ 12,682	$ 12,682