Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Property, Plant and Equipment [Line Items]
Restricted Cash and Cash Equivalents	$ 22,900	$ 30,700
Restricted Cash included in other current assets	2,819	7,900	$ 12,857
Restricted Cash included in other assets	$ 20,124	$ 22,800	$ 11,521