Goodwill and Intangible Assets - Intangible assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Intangible Assets
Gross Value	$ 237,400		$ 237,400		$ 99,509
Accumulated Amortization	(40,981)		(40,981)		(22,303)
Intangible Assets, net	196,419		196,419		$ 77,206
Amortization expense	6,927	$ 2,782	$ 18,678	$ 7,949
Trade name
Intangible Assets
Weighted Average Amortization Period			7 years		8 years
Gross Value	11,625		$ 11,625		$ 7,436
Accumulated Amortization	(3,687)		(3,687)		(2,357)
Intangible Assets, net	7,938		$ 7,938		$ 5,079
Client relationships
Intangible Assets
Weighted Average Amortization Period			12 years 2 months 12 days		9 years 7 months 6 days
Gross Value	128,169		$ 128,169		$ 54,069
Accumulated Amortization	(18,202)		(18,202)		(10,757)
Intangible Assets, net	109,967		$ 109,967		$ 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	(2,941)		(2,941)		(1,885)
Intangible Assets, net	4,313		$ 4,313		$ 4,869
Developed technology
Intangible Assets
Weighted Average Amortization Period			8 years		7 years 2 months 12 days
Gross Value	68,593		$ 68,593		$ 31,191
Accumulated Amortization	(13,606)		(13,606)		(7,296)
Intangible Assets, net	54,987		$ 54,987		$ 23,895
Patient database
Intangible Assets
Weighted Average Amortization Period			5 years
Gross Value	21,700		$ 21,700
Accumulated Amortization	(2,532)		(2,532)
Intangible Assets, net	19,168		$ 19,168
Domain name
Intangible Assets
Weighted Average Amortization Period			10 years		10 years
Gross Value	59		$ 59		$ 59
Accumulated Amortization	(13)		(13)		(8)
Intangible Assets, net	$ 46		$ 46		$ 51