Condensed Consolidated Statement of Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Earnings (Accumulated Deficit) [Member]
Balance at Dec. 31, 2017	$ 2,572,871	$ 871	$ 2,517,545	$ (374,118)	$ 428,573
Balance, shares at Dec. 31, 2017		87,060,000
Common stock issued under stock incentive plans	96	$ 2	94
Common stock issued under stock incentive plans, shares		228,000
Common stock withheld for minimum statutory taxes	(2,126)		(2,126)
Equity-based compensation expense	6,919		6,919
Other comprehensive income (loss)	72,727			72,727
Other	313		313
Net income (Loss) attributable to Acadia Healthcare Company, Inc. stockholders	50,819				50,819
Balance at Mar. 31, 2018	2,701,619	$ 873	2,522,745	(301,391)	479,392
Balance, shares at Mar. 31, 2018		87,288,000
Balance at Dec. 31, 2017	$ 2,572,871	$ 871	2,517,545	(374,118)	428,573
Balance, shares at Dec. 31, 2017		87,060,000
Common stock issued under stock incentive plans, shares	20,989
Balance at Dec. 31, 2018	$ 2,333,307	$ 874	2,541,987	(462,377)	252,823
Balance, shares at Dec. 31, 2018	87,444,473	87,444,000
Balance at Mar. 31, 2018	$ 2,701,619	$ 873	2,522,745	(301,391)	479,392
Balance, shares at Mar. 31, 2018		87,288,000
Common stock issued under stock incentive plans	128		128
Common stock issued under stock incentive plans, shares		42,000
Common stock withheld for minimum statutory taxes	(232)		(232)
Equity-based compensation expense	7,129		7,129
Other comprehensive income (loss)	(114,492)			(114,492)
Other	313		313
Net income (Loss) attributable to Acadia Healthcare Company, Inc. stockholders	58,836				58,836
Balance at Jun. 30, 2018	2,653,301	$ 873	2,530,083	(415,883)	538,228
Balance, shares at Jun. 30, 2018		87,330,000
Common stock issued under stock incentive plans	20	$ 1	19
Common stock issued under stock incentive plans, shares		33,000
Common stock withheld for minimum statutory taxes	(158)		(158)
Equity-based compensation expense	5,225		5,225
Other comprehensive income (loss)	(24,579)			(24,579)
Other	208		208
Net income (Loss) attributable to Acadia Healthcare Company, Inc. stockholders	46,232				46,232
Balance at Sep. 30, 2018	2,680,249	$ 874	2,535,377	(440,462)	584,460
Balance, shares at Sep. 30, 2018		87,363,000
Common stock issued under stock incentive plans	130		130
Common stock issued under stock incentive plans, shares		81,000
Common stock withheld for minimum statutory taxes	(1,265)		(1,265)
Equity-based compensation expense	2,728		2,728
Other comprehensive income (loss)	(21,915)			(21,915)
Other	5,017		5,017
Net income (Loss) attributable to Acadia Healthcare Company, Inc. stockholders	(331,637)				(331,637)
Balance at Dec. 31, 2018	$ 2,333,307	$ 874	2,541,987	(462,377)	252,823
Balance, shares at Dec. 31, 2018	87,444,473	87,444,000
Common stock issued under stock incentive plans	$ 293	$ 2	291
Common stock issued under stock incentive plans, shares	18,315	149,000
Common stock withheld for minimum statutory taxes	$ (1,620)		(1,620)
Equity-based compensation expense	6,101		6,101
Other comprehensive income (loss)	35,791			35,791
Net income (Loss) attributable to Acadia Healthcare Company, Inc. stockholders	29,471				29,471
Balance at Mar. 31, 2019	$ 2,403,343	$ 876	$ 2,546,759	$ (426,586)	$ 282,294
Balance, shares at Mar. 31, 2019	87,593,730	87,593