Significant Accounting Policies (Cash, Cash Equivalents, and Restricted Cash) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Cash and cash equivalents	$ 38,560	$ 58
Restricted cash included in other assets	16,389	15,934	$ 15,400
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 54,949	$ 15,992	$ 17,050	$ 17,502