Revenue Recognition - Changes in Balance of Deferred Revenues (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Revenue Recognition
Beginning balance	$ 28,722	$ 72,930
Increase in deferred revenues	14,974	3,474
Refunds of revenues previously deferred		(10,000)
Revenue recognized during the period that was included in deferred revenues at the beginning of the period	(5,757)	(30,839)
Revenue recognized from performance obligations satisfied within the same period	(1,209)	(1,356)
Ending Balance	$ 36,730	$ 34,209