Goodwill and Intangible Assets - Intangible assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Intangible Assets
Gross Value	$ 236,198		$ 236,198		$ 99,509
Accumulated Amortization	(34,054)		(34,054)		(22,303)
Intangible Assets, net	202,144		202,144		$ 77,206
Amortization expense	7,084	$ 2,639	$ 11,751	$ 5,167
Trade name
Intangible Assets
Weighted Average Amortization Period			6 years 11 months 19 days		7 years 11 months 15 days
Gross Value	11,625		$ 11,625		$ 7,436
Accumulated Amortization	(3,209)		(3,209)		(2,357)
Intangible Assets, net	8,416		$ 8,416		$ 5,079
Client relationships
Intangible Assets
Weighted Average Amortization Period			12 years 2 months 4 days		9 years 6 months 21 days
Gross Value	128,169		$ 128,169		$ 54,069
Accumulated Amortization	(15,426)		(15,426)		(10,757)
Intangible Assets, net	112,743		$ 112,743		$ 43,312
Non-competition agreement
Intangible Assets
Weighted Average Amortization Period			5 years		5 years
Gross Value	7,254		$ 7,254		$ 6,754
Accumulated Amortization	(2,589)		(2,589)		(1,885)
Intangible Assets, net	4,665		$ 4,665		$ 4,869
Developed technology
Intangible Assets
Weighted Average Amortization Period			8 years 1 month 6 days		7 years 2 months 8 days
Gross Value	67,391		$ 67,391		$ 31,191
Accumulated Amortization	(11,371)		(11,371)		(7,296)
Intangible Assets, net	56,020		$ 56,020		$ 23,895
Patient database
Intangible Assets
Weighted Average Amortization Period			5 years
Gross Value	21,700		$ 21,700
Accumulated Amortization	(1,447)		(1,447)
Intangible Assets, net	20,253		$ 20,253
Domain name
Intangible Assets
Weighted Average Amortization Period			10 years		10 years
Gross Value	59		$ 59		$ 59
Accumulated Amortization	(12)		(12)		(8)
Intangible Assets, net	$ 47		$ 47		$ 51