Summary of Significant Accounting Policies - Summary of Revenues Disaggregated by Type of Services (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	[1]	Jun. 30, 2018	Jun. 30, 2017	[1]
Disaggregation Of Revenue [Line Items]
Total Revenue	$ 89,545	$ 74,493		$ 176,311	$ 147,072
Promotion
Disaggregation Of Revenue [Line Items]
Total Revenue	60,912	58,356		124,695	115,702
Media
Disaggregation Of Revenue [Line Items]
Total Revenue	$ 28,633	$ 16,137		$ 51,616	$ 31,370

[1] As noted above, prior period amounts have not been adjusted under the modified retrospective method.