Transactions - Securities Offerings and Sales (Details) - USD ($)	1 Months Ended							12 Months Ended
	May 31, 2019	Nov. 30, 2018	Mar. 31, 2018	Aug. 31, 2017	Jun. 30, 2017	May 31, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Oct. 31, 2019	Apr. 30, 2019	Oct. 31, 2018	Oct. 01, 2018	Sep. 30, 2018	Jun. 30, 2018	Feb. 28, 2018	Jul. 31, 2017	May 30, 2017	Feb. 28, 2017	Jun. 05, 2015
Organization [Line Items]
Share price (in dollars per share)											$ 6.59
Offering expenses								$ 0	$ 0	$ 1,500,000
Class A Common Stock
Organization [Line Items]
Issuance of common stock (in shares)				8,800,000						20,100,000
Common stock, shares outstanding (in shares)								84,588,629	79,172,118
Proceeds from issuance of common stock, net of payments of stock issuance costs				$ 166,900,000
Proceeds from issuance of common stock				$ 175,000,000.0
Class A Common Stock | Evolent Health, Selling Stockholders
Organization [Line Items]
Issuance of common stock (in shares)										7,400,000
Class A Common Stock | Investor Stockholders
Organization [Line Items]
Issuance of common stock (in shares)										12,600,000
Class A Common Stock | Management Selling Stockholders
Organization [Line Items]
Issuance of common stock (in shares)										100,000
Class A Common Stock | Common Stock
Organization [Line Items]
Issuance of common stock (in shares)	1,600,000	800,000	3,000,000.0		4,500,000	7,000,000.0	7,500,000	3,100,000		8,816,000
Share price (in dollars per share)				$ 19.85	$ 25.87	$ 24.30	$ 19.53
Offering expenses				$ 8,100,000
Class A Common Stock | Common Stock | Evolent Health, Selling Stockholders
Organization [Line Items]
Issuance of common stock (in shares)		100,000	1,200,000		700,000	3,100,000	3,100,000
Class A Common Stock | Common Stock | Over-Allotment Option
Organization [Line Items]
Issuance of common stock (in shares)							1,100,000
Share price (in dollars per share)							$ 19.53
Class A Common Stock | Common Stock | Over-Allotment Option | Evolent Health, Selling Stockholders
Organization [Line Items]
Issuance of common stock (in shares)							500,000
Class A Common Stock | Common Stock | The Advisory Board
Organization [Line Items]
Issuance of common stock (in shares)			1,800,000
Common stock, shares outstanding (in shares)																0
Class A Common Stock | Common Stock | TPG
Organization [Line Items]
Issuance of common stock (in shares)		700,000
Common stock, shares outstanding (in shares)								0
Class A Common Stock | Common Stock | Underwriters
Organization [Line Items]
Share price (in dollars per share)				$ 19.01
Class A Common Stock | Common Stock | Investor Stockholders
Organization [Line Items]
Issuance of common stock (in shares)					3,800,000	3,800,000	4,400,000
Class A Common Stock | Common Stock | Investor Stockholders | Over-Allotment Option
Organization [Line Items]
Issuance of common stock (in shares)							600,000
Class A Common Stock | Common Stock | Management Selling Stockholders
Organization [Line Items]
Issuance of common stock (in shares)						100,000
Class B Common Stock
Organization [Line Items]
Common stock, shares outstanding (in shares)								0	3,190,301
Class B Common Stock | Common Stock
Organization [Line Items]
Issuance of common stock (in shares)									3,120,000
Class B Common Stock | Common Stock | TPG
Organization [Line Items]
Common stock, shares outstanding (in shares)								0
Common Class B Units | Common Stock | TPG
Organization [Line Items]
Common stock, shares outstanding (in shares)								0
Evolent Health LLC
Organization [Line Items]
Parent's ownership percentage	99.20%	96.10%	98.90%	96.60%	96.10%	90.50%	83.90%	100.00%	96.10%	77.40%		99.10%	95.30%	95.30%	99.00%		96.60%	96.10%	84.90%	77.40%	70.30%
Evolent Health LLC | Over-Allotment Option
Organization [Line Items]
Parent's ownership percentage							84.90%													83.90%