Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 90,220	$ 89,879	$ 98,821	$ 88,818
Restricted Cash	20,740	21,171	21,458	21,883
Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents	$ 110,960	$ 111,050	$ 120,279	$ 110,701