Revenue - Impact of Adoption on Balance Sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net	$ 19,427	$ 17,375
Prepaid expenses and other current assets	4,386	5,327
Total current assets	146,853	128,794
Other assets	907	223
Total assets	224,237	205,050
Accrued compensation and employee benefits	6,912	6,611
Accounts payable and accrued expenses	8,044	5,273
Deferred revenue	15,087	13,891
Total current liabilities	30,043	25,775
Other liabilities	802	1,776
Total liabilities	33,630	30,916
Retained earnings/(accumulated deficit)	5,076	(6,819)
Total stockholders’ equity	190,607	174,134
Total liabilities and stockholders’ equity	$ 224,237	205,050
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net		17,375
Prepaid expenses and other current assets		5,327
Total current assets		128,794
Deferred tax assets, net		6,124
Other assets		223
Total assets		205,050
Accrued compensation and employee benefits		6,611
Accounts payable and accrued expenses		5,273
Deferred revenue		13,891
Total current liabilities		25,775
Other liabilities		1,776
Total liabilities		30,916
Retained earnings/(accumulated deficit)		(6,819)
Total stockholders’ equity		174,134
Total liabilities and stockholders’ equity		205,050
As Reported | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net		16,399
Prepaid expenses and other current assets		5,102
Total current assets		127,593
Deferred tax assets, net		6,500
Other assets		118
Total assets		204,120
Accrued compensation and employee benefits		6,490
Accounts payable and accrued expenses		5,271
Deferred revenue		14,113
Total current liabilities		25,874
Other liabilities		1,792
Total liabilities		31,031
Retained earnings/(accumulated deficit)		(7,864)
Total stockholders’ equity		173,089
Total liabilities and stockholders’ equity		204,120
Adoption of ASU 2014-09 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net		976
Prepaid expenses and other current assets		225
Total current assets		1,201
Deferred tax assets, net		(376)
Other assets		105
Total assets		930
Accrued compensation and employee benefits		121
Accounts payable and accrued expenses		2
Deferred revenue		(222)
Total current liabilities		(99)
Other liabilities		(16)
Total liabilities		(115)
Retained earnings/(accumulated deficit)		1,045
Total stockholders’ equity		1,045
Total liabilities and stockholders’ equity		$ 930