Nature of Ops and Sign. Acctg Policies (Cash, Cash Equivalents, and Restricted Cash) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents	$ 516	$ 38,560
Restricted cash included in other assets	32,529	16,389
Total cash, cash equivalents, and restricted cash shown in the Consolidated Statements of Cash Flows	$ 33,045	$ 54,949	$ 15,992	$ 17,050