Revenue Recognition - Summary of Impact of Adoption on Consolidated Statement of Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
STATEMENT OF OPERATIONS
Revenue	$ 147,094	$ 104,352	$ 76,846
Net loss	(47,515)	$ (19,634)	$ (11,286)
Accounting Standards Update 2014-09 | Balances Without Adoption of ASC 606
STATEMENT OF OPERATIONS
Revenue	147,094
Net loss	(50,606)
Accounting Standards Update 2014-09 | Effect of Change Higher/(Lower)
STATEMENT OF OPERATIONS
Net loss	$ 3,091