Basis of Presentation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
Basis of Presentation [Line Items]
Cash and cash equivalents	$ 31,631	$ 259,067
Restricted Cash	300	300
Operating lease liability	$ 345
Operating Lease, Liability, Statement of Financial Position [Extensible List]	Liabilities
Operating lease right of use asset	$ 342	988
Special Dividend I [Member]
Basis of Presentation [Line Items]
Dividends payable, date declared	Apr. 30, 2020
Common stock, dividends, per share	$ 5.50
Dividends, cash	$ 170,100
Dividends payable, date paid	May 28, 2020
Dividends payable, date of record	May 14, 2020
Special Dividend II [Member]
Basis of Presentation [Line Items]
Dividends payable, date declared	Nov. 23, 2020
Common stock, dividends, per share	$ 1.50
Dividends, cash	$ 46,400
Dividends payable, date paid	Dec. 17, 2020
Dividends payable, date of record	Dec. 04, 2020
Accounting Standards Update 2016-02 [Member]
Basis of Presentation [Line Items]
Operating lease liability			$ 300
Operating Lease, Liability, Statement of Financial Position [Extensible List]			Liabilities
Operating lease right of use asset			$ 300
Equity Method Investee [Member]
Basis of Presentation [Line Items]
Investments in affiliates, guarantee or other funding obligations	$ 0	$ 0