Basis of Presentation and Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Change in Contract with Customer, Liability [Roll Forward]
Balance at beginning of period	$ 794	$ 968
Previously deferred revenues recognized upon completion of performance obligations during the period	(786)	(950)
Net contract liabilities arising during the period	2,985	2,723
Balance at end of period	$ 2,993	$ 2,741