Goodwill and Intangible Assets - Intangible assets (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Intangible Assets
Gross Value	$ 73,889		$ 73,889
Accumulated Amortization	(13,681)		(11,153)
Intangible Assets, net	60,208		$ 62,736
Amortization expense	$ 2,528	$ 950
Trade names
Intangible Assets
Weighted Average Amortization Period	8 years 6 months 22 days		8 years 6 months 22 days
Gross Value	$ 6,716		$ 6,716
Accumulated Amortization	(1,537)		(1,320)
Intangible Assets, net	$ 5,179		$ 5,396
Client relationships
Intangible Assets
Weighted Average Amortization Period	8 years 5 months 23 days		8 years 5 months 23 days
Gross Value	$ 34,949		$ 34,949
Accumulated Amortization	(6,770)		(5,652)
Intangible Assets, net	$ 28,179		$ 29,297
Non-competition agreement
Intangible Assets
Weighted Average Amortization Period	4 years 11 months 16 days		4 years 11 months 16 days
Gross Value	$ 5,404		$ 5,404
Accumulated Amortization	(1,011)		(739)
Intangible Assets, net	$ 4,393		$ 4,665
Developed technology
Intangible Assets
Weighted Average Amortization Period	7 years 4 months 17 days		7 years 4 months 17 days
Gross Value	$ 26,791		$ 26,791
Accumulated Amortization	(4,358)		(3,438)
Intangible Assets, net	$ 22,433		$ 23,353
Domain name
Intangible Assets
Weighted Average Amortization Period	10 years		10 years
Gross Value	$ 29		$ 29
Accumulated Amortization	(5)		(4)
Intangible Assets, net	$ 24		$ 25