Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net income attributable to Acadia									$ 31,439	$ 61,470	$ 72,776
Less: net income attributable to participating securities									(267)	(642)	(793)
Income from continuing operations net of income attributable to participating securities									$ 31,172	$ 60,828	$ 71,983
Denominator:
Weighted average shares for basic earnings per share (in shares)									82,080,159	83,682,789	76,231,000
Effect of dilutive securities:
Employee unvested restricted shares (in shares)									0	2,682	12,550
Denominator for diluted earnings per share (in shares)	81,591	81,566	81,756	83,438	83,733	83,700	83,662	83,646	82,080,159	83,685,471	76,243,550
Basic and diluted earnings per share (in dollars per share)									$ 0.38	$ 0.73	$ 0.94
Series A Preferred OP Units
Anti-Dilutive Shares Excluded from Denominator:
Antidilutive securities excluded from computation of earnings per share (in shares)									188	188	188
Series A Preferred OP Units - Common Share Equivalent
Anti-Dilutive Shares Excluded from Denominator:
Antidilutive securities excluded from computation of earnings per share (in shares)									25,067	25,067	25,067
Series C Preferred OP Units
Anti-Dilutive Shares Excluded from Denominator:
Antidilutive securities excluded from computation of earnings per share (in shares)									136,593	136,593	141,593
Series C Preferred OP Units - Common Share Equivalent
Anti-Dilutive Shares Excluded from Denominator:
Antidilutive securities excluded from computation of earnings per share (in shares)									474,278	479,978	410,207
Restricted shares
Anti-Dilutive Shares Excluded from Denominator:
Antidilutive securities excluded from computation of earnings per share (in shares)									36,879	41,299	50,156