Basis of Presentation and Accounting Policies - Schedule of Deferred Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Basis Of Presentation And Accounting Policies [Abstract]
Balance at beginning of period	$ 3,307	$ 4,755
Revenues deferred during the period	50	5
Revenues recognized during the period	(730)	(1,495)
Balance at end of period	$ 2,627	$ 3,265