v3.19.1
Selected Quarterly Financial Data (Unaudited) - Selected Quarterly Financial Data (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]                    
Revenue $ 39,779 $ 41,748 $ 41,092 $ 40,730 $ 32,377 $ 32,096 $ 30,017 $ 31,752 $ 163,349 $ 126,242
Cost of revenue 3,075 3,115 2,873 2,615 2,236 1,889 1,884 1,736 11,678 7,745
Loss from operations (7,114) [1] (3,936) [1] (1,627) [1] (1,235) [1] (539) [1] (1,019) [1] (1,580) [1] (1,551) [1] (13,912) (4,689)
Net loss (6,925) [1] (3,808) [1] (1,730) [1] (1,328) [1] (653) [1] (1,135) [1] (1,665) [1] (1,618) [1] (13,791) (5,071)
Net loss attributable to common stockholders $ (6,925) [1] $ (3,808) [1] $ (28,132) [1] $ (12,341) [1] $ (2,498) [1] $ (604) [1] $ (2,660) [1] $ (13,402) [1] $ (51,206) $ (19,164)
Basic and diluted net loss attributable to common stockholders per share [1] $ (0.28) $ (0.15) $ (3.10) $ (1.42) $ (0.29) $ (0.07) $ (0.31) $ (1.45)    
[1] The Company's statements of operations were impacted in the third and fourth quarter of 2018 by the recognition of $0.6 million and $1.1 million of stock-based compensation expense, respectively, related to performance-based RSU grants for which achievement of the performance condition became probable.