Revenue Recognition - Summary of Impact of Adoption of New Revenue Standard on Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 41,107		$ 31,699
Deferred costs	6,503		2,429
Deferred costs (non-current)	10,265
Other current liabilities	1,490		808
Deferred revenue (current and non-current)	95,636		73,072
Accumulated deficit	(147,670)		$ (109,252)
Accounting Standards Update 2014-09
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net		$ 31,799
Deferred costs		4,561
Deferred costs (non-current)		6,965
Other current liabilities		908
Deferred revenue (current and non-current)		73,072
Accumulated deficit		(100,155)
Accounting Standards Update 2014-09 | Adjustments Due to ASC 606
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	200	100
Deferred costs	1,923	2,132
Deferred costs (non-current)	10,265	6,965
Other current liabilities	200	100
Accumulated deficit	12,188	$ 9,097
Accounting Standards Update 2014-09 | Balances Without Adoption of ASC 606
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	40,907
Deferred costs	4,580
Other current liabilities	1,290
Deferred revenue (current and non-current)	95,636
Accumulated deficit	$ (159,858)