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Debt - Mortgages and Other Notes Payable - Additional Information (Details) $ in Thousands			3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 29, 2021	Oct. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) Mortgage	Jun. 30, 2021 USD ($) Mortgage	Dec. 31, 2020 USD ($) Mortgage	Jul. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)	Feb. 29, 2020 USD ($)
Debt Instrument [Line Items]
Notes receivable, net			$ 101,450	$ 117,280	$ 101,450
Maximum borrowing capacity				$ 900,000
Mortgages
Debt Instrument [Line Items]
Number of mortgage loans \| Mortgage				7
Number of properties collateralized \| Mortgage			42	37	42
Mortgages \| Subscription Line
Debt Instrument [Line Items]
Number of mortgage loans \| Mortgage					7
Notes receivable, net			$ 46,000	$ 125,300	$ 46,000
Mortgages \| Subscription Line 1
Debt Instrument [Line Items]
Notes receivable, net			51,300		51,300
Mortgages \| Subscription Line 2
Debt Instrument [Line Items]
Notes receivable, net			40,000	25,900	40,000
Mortgages \| Subscription Line 3
Debt Instrument [Line Items]
Notes receivable, net			88,000	12,000	88,000
Fund IV
Debt Instrument [Line Items]
Repayments of debt				23,500
Fund IV \| Bridge Facility
Debt Instrument [Line Items]
Maximum borrowing capacity				79,200
Repayments of debt				$ 10,000
Maturity date	Jun. 30, 2021			Dec. 31, 2021
LIBOR plus	2.00%			2.50%
LIBOR floor				0.25%
Fund IV \| Mortgages
Debt Instrument [Line Items]
Holdback mortgage loan			23,800		23,800
Holdback mortgage loan outstanding			18,900		18,900
Holdback mortgage loan drew an additional						$ 900	$ 1,000
Fund IV \| Mortgages One \| Colonie Plaza - Albany, NY
Debt Instrument [Line Items]
Repayments of debt					11,600
Fund V \| Mortgages
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 4,600
Maturity date				May 02, 2022
LIBOR plus	1.60%			1.90%
Core Portfolio
Debt Instrument [Line Items]
Notes receivable, net				$ 16,000
Repayments of debt					26,300
Derivative, notional amount				539,898
Core Portfolio \| Sixty Orange Street \| Disposed of by sale
Debt Instrument [Line Items]
Repayments of debt				6,700
Scheduled principal payment				4,000
Core Portfolio \| Mortgages \| Brandywine Portfolio
Debt Instrument [Line Items]
Debt default, amount				$ 26,300
Debt instrument, maturity date				Jul. 01, 2016
Gain (loss) on litigation settlement		$ 30,000
Acquisition of noncontrolling interest		$ 15,900
Core Portfolio \| Mortgages \| Brandywine Portfolio \| Acadia's OP Ownership
Debt Instrument [Line Items]
Equity interest held by Operating Partnership		77.78%
Core Portfolio \| Mortgages \| Realized and Unrealized Holding Gains on Investments and Other \| Brandywine Portfolio
Debt Instrument [Line Items]
Gain on debt extinguishment			18,300
Proportionate share		$ 4,100
Fund II \| Mortgages
Debt Instrument [Line Items]
Notes receivable, net			200,000		200,000
Fund III and Fund IV \| Mortgages
Debt Instrument [Line Items]
Holdback mortgage loan			103,400		103,400
Fund Loans Repaid			11,500		11,500
Interest Rate Swaps
Debt Instrument [Line Items]
Derivative, notional amount			$ 30,400		$ 30,400			$ 50,000
Interest Rate Swaps \| New Towne Plaza
Debt Instrument [Line Items]
Derivative, notional amount				$ 16,700
Cash proceeds from swaps				$ 3,400