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
	Mar. 31, 2019	Mar. 31, 2018
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Current portion of prepaid commission expense	$ 59
Prepaid commission expense	456
Sales and marketing	9,592	$ 8,109
Net loss	(7,529)	$ (5,497)
ASC 606 | Income Statement
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Sales and marketing	9,592
Net loss	(7,529)
ASC 606 | Income Statement | Balance Without Adoption of ASC 606
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Sales and marketing	10,107
Net loss	(8,044)
ASC 606 | Income Statement | Effect of Change Higher/(Lower)
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Sales and marketing	(515)
Net loss	515
Balance Sheet | ASC 606
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Current portion of prepaid commission expense	59
Prepaid commission expense	456
Balance Sheet | ASC 606 | Effect of Change Higher/(Lower)
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Current portion of prepaid commission expense	59
Prepaid commission expense	$ 456