Segment Reporting and Significant Customer Information - Revenue by Type and Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Breakdown of revenues by type and segment
Total revenues	$ 28,075	$ 26,411	$ 58,959	$ 54,840
Asia Pacific
Breakdown of revenues by type and segment
Total revenues	2,064	1,950	4,086	3,763
Europe
Breakdown of revenues by type and segment
Total revenues	8,500	7,897	18,780	16,968
North America
Breakdown of revenues by type and segment
Total revenues	17,511	16,564	36,093	34,109
Travel
Breakdown of revenues by type and segment
Total revenues	23,935	22,564	50,925	47,095
Travel | Asia Pacific
Breakdown of revenues by type and segment
Total revenues	1,930	1,858	3,831	3,525
Travel | Europe
Breakdown of revenues by type and segment
Total revenues	7,409	6,795	16,462	14,801
Travel | North America
Breakdown of revenues by type and segment
Total revenues	14,596	13,911	30,632	28,769
Local
Breakdown of revenues by type and segment
Total revenues	4,140	3,847	8,034	7,745
Local | Asia Pacific
Breakdown of revenues by type and segment
Total revenues	134	92	255	238
Local | Europe
Breakdown of revenues by type and segment
Total revenues	1,091	1,102	2,318	2,167
Local | North America
Breakdown of revenues by type and segment
Total revenues	$ 2,915	$ 2,653	$ 5,461	$ 5,340