Equity Investees (Schedule of Balance Sheet Information for Equity Investees) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Assets
Current assets	$ 15,979	$ 18,711
Fixed assets, net	209,728	217,343
Other assets	1,044	1,203
Total assets	226,751	237,257
Liabilities and equity
Current liabilities	18,244	17,560
Other liabilities	241,134	237,434
Equity	(32,627)	(17,737)
Total liabilities and equity	$ 226,751	$ 237,257