Organization (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Aug. 31, 2017	Jul. 31, 2017	Jun. 30, 2017	Jun. 29, 2017	May 31, 2017	May 30, 2017	Mar. 31, 2017	Feb. 28, 2017	Dec. 31, 2016	Sep. 30, 2016	Sep. 22, 2016	Sep. 21, 2016	Dec. 31, 2015	Jun. 05, 2015
Organization [Line Items]
Cash and cash equivalents	$ 287,143									$ 134,563	$ 109,777			$ 145,726
Evolent Health LLC | Pre-Organization Members
Organization [Line Items]
Evolent Health LLC ownership interest	100.00%
Evolent Health LLC
Organization [Line Items]
Parent's ownership percentage	96.60%	96.60%	96.10%	96.10%	90.50%	90.50%	84.90%	83.90%	77.40%	77.40%		74.60%	71.00%		70.30%