Schedule II Valuation of Qualifying Accounts and Reserves (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation Allowances and Reserves, Balance Beginning of Period	$ 1,475	$ 1,475	$ 1,475
Valuation Allowances and Reserves, Charged to Cost and Expense	0	0	0
Valuation Allowances and Reserves, Charged to Other Accounts	0	0	0
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction	575	0	0
Valuation Allowances and Reserves, Balance End of Period	$ 900	$ 1,475	$ 1,475