Earnings (Loss) Per Common Share - Computation of Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Class of Stock [Line Items]
Net loss	$ (78,752)	$ (48,649)
Less:
Net loss attributable to non-controlling interests	0	(1,910)
Net loss attributable to common shareholders of Evolent Health, Inc.	$ (78,752)	$ (46,739)
Weighted-average common shares outstanding - Basic and diluted (in shares)	84,793,000	79,335,000
Loss per common share
Basic and diluted (in dollars per share)	$ (0.93)	$ (0.59)
Class B Common Stock
Loss per common share
Convertible preferred stock, shares issued upon conversion (in shares)	1