Description of Business and Summary of Significant Accounting Policies (Cash, Cash Equivalents, and Restricted Cash Shown in the Statement of Cash Flows) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Cash and cash equivalents	$ 147,766	$ 63,895	$ 114,118
Restricted Cash and Cash Equivalents, Current	8,317	4,040	0
Restricted Cash, Noncurrent	3,506	2,932	2,823
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 159,589	$ 70,867	$ 116,941	$ 57,179