Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator:
Net income attributable to Acadia	$ 12,867	$ 6,112	$ 40,558	$ 52,955
Less: net income attributable to participating securities	(135)	(58)	(488)	(617)
Income from continuing operations net of income attributable to participating securities	$ 12,732	$ 6,054	$ 40,070	$ 52,338
Denominator:
Weighted average shares for basic earnings per share	83,699,850	78,448,643	83,665,749	74,049,523
Effect of dilutive securities:
Employee unvested restricted shares	0	3,034	3,577	7,861
Future equity issuance	0	169,020	0	75,582
Weighted Average Number of Shares Outstanding, Diluted	83,699,850	78,620,697	83,669,326	74,132,966
Basic and diluted earnings per Common Share from continuing operations attributable to Acadia	$ 0.15	$ 0.08	$ 0.48	$ 0.71
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	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	25,067
Series C Preferred OP Units
Anti-Dilutive Shares Excluded from Denominator:
Antidilutive securities excluded from computation of earnings per share (in shares)	140,343	141,593	140,343	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)	487,299	402,252	481,878	402,519