Non-controlling Interests (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		1 Months Ended		3 Months Ended		12 Months Ended
	Jun. 05, 2015	Mar. 31, 2017	Sep. 30, 2016	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Mar. 30, 2017	Dec. 30, 2016	Sep. 19, 2016	Sep. 18, 2016	Dec. 31, 2015	Sep. 30, 2015
Noncontrolling Interest [Line Items]
Share price (in usd per share)					$ 10.33						$ 14.73	$ 19.51
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Non-controlling interests as of beginning-of-period				$ 209,588
Cumulative-effect adjustment from adoption of new accounting principle						$ 0
Reclassification of non-controlling interests				0		0
Net income (loss) attributable to non-controlling interests				(5,137)	$ (51,071)
Non-controlling interests as of end-of-period		$ 146,269		$ 146,269		$ 209,588
Evolent Health LLC
Noncontrolling Interest [Line Items]
Parent's ownership percentage	70.30%	83.90%		83.90%		77.40%	77.40%		74.60%	71.00%
Evolent Health LLC | Passport
Noncontrolling Interest [Line Items]
Parent's ownership percentage						70.80%		70.30%
Evolent Health LLC | Valence Health and Aldera
Noncontrolling Interest [Line Items]
Parent's ownership percentage						77.40%		74.60%
Common Stock | Class A
Noncontrolling Interest [Line Items]
Issuance of common stock (in shares)	13,200	7,500	8,600
Issuance of common stock for business combinations (in shares)	2,100					8,451
Share price (in usd per share)	$ 17.00	$ 19.53	$ 22.50	$ 19.53
Common Stock | Class A | Investor Stockholders
Noncontrolling Interest [Line Items]
Issuance of common stock (in shares)		4,400	2,200
Common Stock | Class A | Evolent Health, Selling Stockholders
Noncontrolling Interest [Line Items]
Issuance of common stock (in shares)		3,100	6,400
Non-controlling Interests
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Non-controlling interests as of beginning-of-period				$ 209,588	285,238	$ 285,238
Cumulative-effect adjustment from adoption of new accounting principle				0	(139)	(139)
Decrease in non-controlling interests as a result of the exchange of Class B common stock for Class A common stock as part of the March Secondary Offering				(59,585)	0
Reclassification of non-controlling interests				1,403	0	19,745
Net income (loss) attributable to non-controlling interests				(5,137)	(51,071)
Non-controlling interests as of end-of-period		$ 146,269		$ 146,269	$ 234,028	$ 209,588