Basis of Presentation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	Nov. 23, 2020	Apr. 30, 2020	Sep. 30, 2021	Dec. 31, 2020
Basis of Presentation [Line Items]
Cash and cash equivalents			$ 19,986	$ 31,631
Restricted Cash			300	300
Equity Method Investee [Member]
Basis of Presentation [Line Items]
Investments in affiliates, guarantee or other funding obligations			$ 0	$ 0
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