Basis of Presentation (Narrative) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018	Jun. 30, 2018
Basis of Presentation [Line Items]
Cash and cash equivalents	$ 257,686		$ 256,947	$ 250,137
Restricted cash	304			$ 304
Investments in affiliates, guarantee or other funding obligations	0		$ 0
Operating lease liability		$ 300
Right-of-use asset	$ 661	300
Accounting Standards Update 2016-02 [Member] | Restatement Adjustment [Member]
Basis of Presentation [Line Items]
Operating lease liability		300
Right-of-use asset		$ 300