Quarterly Results of Operations (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								7 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Total revenue	$ 113,729	$ 107,912	$ 107,071	$ 106,238	$ 88,011	$ 60,210	$ 56,518	$ 49,449		$ 434,950	$ 254,188	$ 96,878
Total operating expenses	131,977	121,932	126,188	127,693	121,884	76,049	69,147	224,527		507,790	491,607	139,850
Net income (loss)	(13,791)	(13,129)	(19,698)	(23,149)	(25,193)	(15,775)	(11,999)	(173,811)	$ 347,979	(69,767)	(226,778)	319,814
Net income (loss) attributable to non-controlling interests	(631)	(541)	(2,793)	(5,137)	(7,786)	(4,567)	(3,612)	(51,071)		(9,102)	(67,036)	(12,680)
Net income (loss) attributable to Evolent Health, Inc.	$ (13,160)	$ (12,588)	$ (16,905)	$ (18,012)	$ (17,407)	$ (11,208)	$ (8,387)	$ (122,740)		$ (60,665)	$ (159,742)	$ 332,494
Earnings (Loss) per Common Share
Basic (in dollars per share)	$ (0.18)	$ (0.18)	$ (0.28)	$ (0.34)	$ (0.33)	$ (0.26)	$ (0.20)	$ (2.91)		$ (0.94)	$ (3.55)	$ 13.14
Diluted (in dollars per share)	$ (0.18)	$ (0.18)	$ (0.28)	$ (0.34)	$ (0.33)	$ (0.26)	$ (0.20)	$ (2.91)		$ (0.94)	$ (3.55)	$ 6.93