Revenue Recognition - Activity of Deferred Contract Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Capitalized Contract Cost [Roll Forward]
Beginning balance	$ 71,768	$ 61,866	$ 72,265	$ 59,434
Capitalization of contract acquisition costs	8,301	9,612	23,314	24,846
Amortization of deferred contract acquisition costs	(8,185)	(6,955)	(23,695)	(19,757)
Ending balance	$ 71,884	$ 64,523	$ 71,884	$ 64,523