Revenue, Deferred Revenue and Prepaid Commissions - Deferred Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Contract With Customer, Asset And Liability [Roll Forward]
Beginning balance	$ 26,582
Additions	42	$ (866)	$ 2,579
Ending balance	26,621	$ 26,582
Accounting Standards Update 2014-09
Contract With Customer, Asset And Liability [Roll Forward]
Additions	70,684
Revenue Recognized	$ (70,645)