Equity Method Investments Summarized Financial Information (Details) - Joint Ventures - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Current assets	$ 15,450	$ 12,671
Non-current assets	240,852	244,329
Current liabilities	4,362	1,798
Revenues	35,050	28,805	$ 2,217
Gross profit	17,690	13,344	(2,048)
Net Income/loss	$ 15,701	$ 10,714	$ (3,641)