Investment in Investee Investment in Investee (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2018	Sep. 30, 2017
Schedule of Equity Method Investments [Line Items]
Equity in net (loss) income of investee				$ (2,499)	$ 2,115
Dividend received from investee				780	0
Proceeds from sale of investee				1,001	0
Proceeds from sale of investee				3,470
Corporate Segment [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investments, Fair Value Disclosure	$ 951		$ 951	951				$ 3,816
Equity in net (loss) income of investee				(2,499)	2,115	$ 2,115
Equity Method Investment, Ownership Percentage	22.90%		22.90%					31.20%
Dividend received from investee				$ 780	$ 0
Subsidiary or Equity Method Investee, Cumulative Number of Shares Issued for All Transactions			6,799,449
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity							$ 1,300
Management [Member]
Schedule of Equity Method Investments [Line Items]
Sale of Stock, Consideration Received on Transaction	$ 1,000	$ 300