Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Finite Lived Intangible Assets [Line Items]
Gross	$ 73,524	$ 73,524
Accumulated Amortization	(29,872)	(27,034)
Net	$ 43,652	$ 46,490
Weighted Average Amortization Period (Years)	4 years 6 months	4 years 8 months 12 days
Promotion Service Rights
Finite Lived Intangible Assets [Line Items]
Gross	$ 22,492	$ 22,492
Accumulated Amortization	(4,991)	(4,252)
Net	$ 17,501	$ 18,240
Weighted Average Amortization Period (Years)	5 years 9 months 18 days	6 years 1 month 6 days
Data Access Rights
Finite Lived Intangible Assets [Line Items]
Gross	$ 10,801	$ 10,801
Accumulated Amortization	(3,129)	(2,666)
Net	$ 7,672	$ 8,135
Weighted Average Amortization Period (Years)	4 years 1 month 6 days	4 years 3 months 18 days
Customer Relationships
Finite Lived Intangible Assets [Line Items]
Gross	$ 11,660	$ 11,660
Accumulated Amortization	(6,979)	(6,547)
Net	$ 4,681	$ 5,113
Weighted Average Amortization Period (Years)	4 years 1 month 6 days	4 years 3 months 18 days
Developed Technologies
Finite Lived Intangible Assets [Line Items]
Gross	$ 12,187	$ 12,187
Accumulated Amortization	(5,656)	(5,013)
Net	$ 6,531	$ 7,174
Weighted Average Amortization Period (Years)	2 years 9 months 18 days	3 years
Media Service Rights
Finite Lived Intangible Assets [Line Items]
Gross	$ 6,383	$ 6,383
Accumulated Amortization	(1,849)	(1,575)
Net	$ 4,534	$ 4,808
Weighted Average Amortization Period (Years)	4 years 1 month 6 days	4 years 3 months 18 days
Domain Names
Finite Lived Intangible Assets [Line Items]
Gross	$ 5,949	$ 5,949
Accumulated Amortization	(4,839)	(4,689)
Net	$ 1,110	$ 1,260
Weighted Average Amortization Period (Years)	1 year 1 month 6 days	1 year 3 months 18 days
Patents
Finite Lived Intangible Assets [Line Items]
Gross	$ 975	$ 975
Accumulated Amortization	(782)	(769)
Net	$ 193	$ 206
Weighted Average Amortization Period (Years)	4 years 2 months 12 days	4 years 6 months
Vendor Relationships
Finite Lived Intangible Assets [Line Items]
Gross	$ 890	$ 890
Accumulated Amortization	(890)	(890)
Registered Users
Finite Lived Intangible Assets [Line Items]
Gross	420	420
Accumulated Amortization	(257)	(232)
Net	$ 163	$ 188
Weighted Average Amortization Period (Years)	1 year 10 months 24 days	2 years 2 months 12 days
Trade Names
Finite Lived Intangible Assets [Line Items]
Gross	$ 1,767	$ 1,767
Accumulated Amortization	(500)	(401)
Net	$ 1,267	$ 1,366
Weighted Average Amortization Period (Years)	3 years 2 months 12 days	3 years 4 months 24 days