Segment Reporting (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment									3
Revenues	$ 66,081	$ 62,678	$ 59,504	$ 61,999	$ 54,121	$ 43,855	$ 43,918	$ 48,045	$ 250,262	$ 189,939	$ 199,063
Depreciation and amortization									(104,934)	(70,011)	(60,751)
Property operating expenses, other operating and real estate taxes									(79,798)	(57,391)	(58,482)
Impairment charges	(10,600)	(3,800)							(14,455)	0	(5,000)
General and administrative expenses									(33,756)	(40,648)	(30,368)
Operating income									17,319	21,889	44,462
Gain on disposition of properties									48,886	81,965	89,063
Interest income									29,143	25,829	16,603
Equity in earnings (losses) of unconsolidated affiliates									23,371	39,449	37,330
Other											1,596
Interest expense									(58,978)	(34,645)	(37,297)
Gain on change in control									5,571	0	0
Income tax (provision) benefit									(1,004)	105	(1,787)
Net income	24,944	13,285	6,108	19,971	34,236	326	26,155	73,875	64,308	134,592	149,970
Net income attributable to noncontrolling interests	(4,032)	(418)	5,952	(4,340)	(14,415)	5,786	(8,237)	(44,950)	(2,838)	(61,816)	(84,262)
Net income attributable to Acadia	20,912	$ 12,867	$ 12,060	$ 15,631	19,821	$ 6,112	$ 17,918	$ 28,925	61,470	72,776	65,708
Real estate at cost	3,466,482				3,382,000				3,466,482	3,382,000	2,736,283
Total assets	3,960,247				3,995,960				3,960,247	3,995,960	3,032,319
Cash paid for acquisition of real estate									200,429	495,644	338,700
Cash paid for development and property improvement costs									115,455	149,434	164,315
Operating segments | Core Portfolio
Segment Reporting Information [Line Items]
Revenues									169,975	150,211	150,015
Depreciation and amortization									(61,705)	(54,582)	(46,223)
Property operating expenses, other operating and real estate taxes									(45,349)	(39,598)	(37,259)
Impairment charges									0		(5,000)
General and administrative expenses									0	0	0
Operating income									62,921	56,031	61,533
Gain on disposition of properties									0	0	0
Interest income									0	0	0
Equity in earnings (losses) of unconsolidated affiliates									3,735	3,774	1,169
Other											0
Interest expense									(28,618)	(27,435)	(27,945)
Gain on change in control									5,571
Income tax (provision) benefit									0	0	0
Net income									43,609	32,370	34,757
Net income attributable to noncontrolling interests									(1,107)	(3,411)	(140)
Net income attributable to Acadia									42,502	28,959	34,617
Real estate at cost	2,032,485				1,982,763				2,032,485	1,982,763	1,572,681
Total assets	2,305,663				2,271,620				2,305,663	2,271,620	1,662,092
Cash paid for acquisition of real estate									0	323,880	181,884
Cash paid for development and property improvement costs									49,339	13,434	16,505
Operating segments | Funds
Segment Reporting Information [Line Items]
Revenues									80,287	39,728	49,048
Depreciation and amortization									(43,229)	(15,429)	(14,528)
Property operating expenses, other operating and real estate taxes									(34,449)	(17,793)	(21,223)
Impairment charges									(14,455)		0
General and administrative expenses									0	0	0
Operating income									(11,846)	6,506	13,297
Gain on disposition of properties									48,886	81,965	89,063
Interest income									0	0	0
Equity in earnings (losses) of unconsolidated affiliates									19,636	35,675	36,161
Other											0
Interest expense									(30,360)	(7,210)	(9,352)
Gain on change in control									0
Income tax (provision) benefit									0	0	0
Net income									26,316	116,936	129,169
Net income attributable to noncontrolling interests									(1,731)	(58,405)	(84,122)
Net income attributable to Acadia									24,585	58,531	45,047
Real estate at cost	1,433,997				1,399,237				1,433,997	1,399,237	1,163,602
Total assets	1,500,755				1,448,177				1,500,755	1,448,177	1,223,039
Cash paid for acquisition of real estate									200,429	171,764	156,816
Cash paid for development and property improvement costs									66,116	136,000	147,810
Operating segments | Structured Financing
Segment Reporting Information [Line Items]
Revenues									0	0	0
Depreciation and amortization									0	0	0
Property operating expenses, other operating and real estate taxes									0	0	0
Impairment charges									0		0
General and administrative expenses									0	0	0
Operating income									0	0	0
Gain on disposition of properties									0	0	0
Interest income									29,143	25,829	16,603
Equity in earnings (losses) of unconsolidated affiliates									0	0	0
Other											1,596
Interest expense									0	0	0
Gain on change in control									0
Income tax (provision) benefit									0	0	0
Net income									29,143	25,829	18,199
Net income attributable to noncontrolling interests									0	0	0
Net income attributable to Acadia									29,143	25,829	18,199
Real estate at cost	0				0				0	0	0
Total assets	153,829				276,163				153,829	276,163	147,188
Cash paid for acquisition of real estate									0	0	0
Cash paid for development and property improvement costs									0	0	0
Unallocated
Segment Reporting Information [Line Items]
Revenues									0	0	0
Depreciation and amortization									0	0	0
Property operating expenses, other operating and real estate taxes									0	0	0
Impairment charges									0		0
General and administrative expenses									(33,756)	(40,648)	(30,368)
Operating income									(33,756)	(40,648)	(30,368)
Gain on disposition of properties									0	0	0
Interest income									0	0	0
Equity in earnings (losses) of unconsolidated affiliates									0	0	0
Other											0
Interest expense									0	0	0
Gain on change in control									0
Income tax (provision) benefit									(1,004)	105	(1,787)
Net income									(34,760)	(40,543)	(32,155)
Net income attributable to noncontrolling interests									0	0	0
Net income attributable to Acadia									(34,760)	(40,543)	(32,155)
Real estate at cost	0				0				0	0	0
Total assets	$ 0				$ 0				0	0	0
Cash paid for acquisition of real estate									0	0	0
Cash paid for development and property improvement costs									$ 0	$ 0	$ 0