Basis of Presentation and Summary of Significant Accounting Policies - Summary of Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Contract assets:
Beginning balance	$ 1,956	$ 739
Additions	8,958	7,117
Deductions	(6,911)
Ending balance	4,003	1,956
Contract liabilities:
Beginning balance	1,280	100
Additions	2,810	4,428
Deductions	(2,761)	(3,248)
Ending balance	1,329	1,280
Amounts reclassified from unbilled revenue to accounts receivable	6,900	5,900
Amounts reclassified from deferred revenue to revenue	$ 2,800	$ 3,200