Description of Business and Basis of Presentation - Summary of Consolidated Balance Sheet Reflecting Adoption of Topic 606 (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets
Accounts receivable—net of allowance	$ 47,510	$ 34,312
Deferred commissions	8,126	7,086
Deferred commissions, net of current portion	11,292	11,160
Other assets	526	497
Liabilities
Deferred revenue	136,179	99,773
Deferred revenue, net of current portion	$ 2,494	1,889
As Previously Reported | Adoption of New Standard
Assets
Accounts receivable—net of allowance		30,797
Other assets		1,045
Liabilities
Deferred revenue		99,086
Deferred revenue, net of current portion		3,950
Adjustments | Adoption of New Standard
Assets
Accounts receivable—net of allowance		3,515
Deferred commissions		7,086
Deferred commissions, net of current portion		11,160
Other assets		(548)
Liabilities
Deferred revenue		687
Deferred revenue, net of current portion		$ (2,061)