Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Basic and diluted earnings per share attributable to Acadia Healthcare Company, Inc.:
Income from continuing operations	$ 56,445	$ 33,843	$ 82,133	$ 48,435
Income from discontinued operations		1		3
Net income attributable to Acadia Healthcare Company, Inc.	$ 56,445	$ 33,844	$ 82,133	$ 48,438
Denominator:
Weighted average shares outstanding for basic earnings per share	86,553	68,296	84,748	65,429
Effect of dilutive instruments	323	439	304	353
Shares used in computing diluted earnings per common share	86,876	68,735	85,052	65,782
Basic earnings per share:
Income from continuing operations	$ 0.65	$ 0.50	$ 0.97	$ 0.74
Income from discontinued operations	0	0	0	0
Net income	0.65	0.50	0.97	0.74
Diluted earnings per share:
Income from continuing operations	0.65	0.49	0.97	0.74
Income from discontinued operations	0	0	0	0
Net income	$ 0.65	$ 0.49	$ 0.97	$ 0.74