Summary of Significant Accounting Policies - Summary of Impact of Adoption on Prepaid Commissions Expense on Balance Sheet and Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Current portion of prepaid commission expense	$ 689								$ 689
Prepaid commission expense	3,779								3,779
Sales and marketing	11,516	$ 10,362	$ 11,523	$ 9,592	$ 10,648	$ 9,672	$ 9,835	$ 8,109	42,993	$ 38,264	$ 27,900
Net loss	(7,554)	$ (6,867)	$ (7,094)	$ (7,529)	$ (6,143)	$ (4,961)	$ (7,496)	$ (5,497)	(29,044)	$ (24,097)	$ (16,059)
ASC 606 | Income Statement
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Sales and marketing									42,993
Net loss									(29,044)
ASC 606 | Income Statement | Balance Without Adoption of ASC 606
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Sales and marketing									47,461
Net loss									(33,512)
ASC 606 | Income Statement | Effect of Change Higher/(Lower)
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Sales and marketing									(4,468)
Net loss									4,468
ASC 606 | Balance Sheet
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Current portion of prepaid commission expense	689								689
Prepaid commission expense	3,779								3,779
ASC 606 | Balance Sheet | Effect of Change Higher/(Lower)
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Current portion of prepaid commission expense	689								689
Prepaid commission expense	$ 3,779								$ 3,779