Debt - Mortgage Payable - Additional Information (Details)					3 Months Ended	12 Months Ended
	Oct. 30, 2020 USD ($)	Oct. 02, 2020	Jun. 24, 2020 USD ($)	Nov. 09, 2017 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2020 USD ($) property loan	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($) property loan	Dec. 31, 2012 USD ($)	Jul. 31, 2020 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Notes receivable, net						$ 101,450,000		$ 114,943,000			$ 111,775,000	$ 160,991,000
Scheduled principal payment						6,100,000
Amount of share failed to meet liquidity requirements.						27,100,000
Mortgages failed to meet debt yield and debt service coverage ratio						124,100,000
Amount of share failed to meet debt yield and debt service coverage ratio						25,600,000
Gain on debt extinguishment						18,339,000
Acquisition of noncontrolling interest						588,000
Interest Rate Swaps
Debt Instrument [Line Items]
Derivative, notional amount						$ 50,000,000.0				$ 30,400,000
Mortgages
Debt Instrument [Line Items]
Scheduled principal payment								5,900,000
Borrowings, amount								$ 258,900,000
Number of properties collateralized | property						42		44
Mortgages | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate								1.70%
Mortgages | Subscription Line
Debt Instrument [Line Items]
Notes receivable, net						$ 46,000,000.0
Number of mortgage loans | loan						7
Mortgages | Subscription Line 1
Debt Instrument [Line Items]
Notes receivable, net						$ 51,300,000
Mortgages | Subscription Line 2
Debt Instrument [Line Items]
Notes receivable, net						40,000,000.0
Mortgages | Subscription Line 3
Debt Instrument [Line Items]
Notes receivable, net						$ 88,000,000.0
Mortgages | Maturing from May 2019 to January 2021
Debt Instrument [Line Items]
Number of mortgage loans | loan								3
Borrowings, amount								$ 69,000,000.0
Mortgages | Maturing from May 2019 to January 2021 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate								2.08%
Mortgages | Maturing from April 2022 though December 2024.
Debt Instrument [Line Items]
Borrowings, amount								$ 71,800,000
Mortgages | Maturing from April 2022 though December 2024. | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate								1.86%
Mortgages | Maturities Ranging from November 2019 through January 2020
Debt Instrument [Line Items]
Number of mortgage loans | loan								3
Borrowings, amount								$ 135,900,000
Mortgages | Maturities Ranging from November 2019 through January 2020 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate								3.65%
Mortgages | Maturing Ranging from December 2020 though May 2021
Debt Instrument [Line Items]
Borrowings, amount								$ 125,300,000
Mortgages | Maturing Ranging from December 2020 though May 2021 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate								2.96%
Mortgages | Interest Rate Swaps
Debt Instrument [Line Items]
Derivative, notional amount								$ 283,600,000
Derivative weighted average interest rate								1.78%
Fund II | New Market Tax Credit
Debt Instrument [Line Items]
Percentage of tax credits on qualifying invested equity loans					39.00%
Transfer of tax credit transactions to investors exchange amount									$ 5,200,000
Redemption of loan expiration period						7 years
Fund II | Realized and Unrealized Holding Gains on Investments and Other | New Market Tax Credit
Debt Instrument [Line Items]
Income recognized from tax credit transactions						$ 5,000,000.0		$ 1,400,000
Fund II | City Point Project | New Market Tax Credit
Debt Instrument [Line Items]
Income recognized from tax credit transactions					$ 5,000,000.0
Fund II | Mortgages
Debt Instrument [Line Items]
Notes receivable, net						200,000,000.0
Number of mortgage loans | loan								1
Fund IV | Mortgages
Debt Instrument [Line Items]
Number of mortgage loans | loan								3
Holdback mortgage loan						23,800,000
Holdback mortgage loan outstanding						18,900,000
Holdback mortgage loan drew an additional						1,000,000.0				$ 900,000
Repayments of debt								$ 38,200,000
Fund IV | Mortgages | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate								2.35%
Fund IV | Mortgages One | Colonie Plaza - Albany, NY
Debt Instrument [Line Items]
Repayments of debt						11,600,000
Fund IV | Mortgages Two
Debt Instrument [Line Items]
Repayments of debt								$ 18,400,000
Fund III and Fund IV | Mortgages
Debt Instrument [Line Items]
Holdback mortgage loan						103,400,000
Fund loans repaid						11,500,000
Core Portfolio
Debt Instrument [Line Items]
Derivative, notional amount						572,148,000
Repayments of debt						$ 26,300,000
Core Portfolio | Mortgages | Brandywine Portfolio
Debt Instrument [Line Items]
Debt default, amount								$ 26,300,000
Debt instrument, maturity date						Jul. 01, 2016
Interest rate, stated percentage						6.00%
Debt default interest						5.00%
Claim amount exclusive of accruing interest, default interest, late charges, and fees and costs				$ 33,000,000.0
Increase the alleged balance			$ 46,800,000
Default interest			300,000
Attorneys fees			200,000
Suspense funds			1,500,000				$ 1,300,000
Parties jointly and severally liable amount			33,200,000
Default interest per diem			$ 8,017
Legal and other costs							6,800,000
Proportionate share							$ 1,500,000
Cross appeal stay period		90 days
Gain (loss) on litigation settlement	$ 30,000,000.0
Acquisition of noncontrolling interest	15,900,000
Core Portfolio | Mortgages | Brandywine Portfolio | Realized and Unrealized Holding Gains on Investments and Other
Debt Instrument [Line Items]
Proportionate share	4,100,000
Gain on debt extinguishment	$ 18,300,000
Core Portfolio | Mortgages | Brandywine Portfolio | Acadia's OP Ownership
Debt Instrument [Line Items]
Equity interest held by Operating Partnership	78.22%
Fund V | Mortgages
Debt Instrument [Line Items]
Number of mortgage loans | loan								5
Fund III | Mortgages
Debt Instrument [Line Items]
Repayments of debt								$ 4,700,000
Fund III | Mortgages | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate								0.50%
Fund III | Mortgages One
Debt Instrument [Line Items]
Repayments of debt								$ 9,800,000
Fund Mortgage And Fund I V
Debt Instrument [Line Items]
Term loans failed to meet liquidity requirements						$ 115,200,000