Schedule II - Valuation and Qualifying Accounts (Details) - Allowance for Doubtful Accounts: - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at the Beginning of the Year ($)	$ 32	$ 22
Charged to Expense ($)	0	10
Acquisitions/ Transfers and Other ($)	0	0
Write-offs Net of Recoveries ($)	(32)	0
Balance at the End of the Year ($)	$ 0	$ 32