Debt - Summary of Consolidated Indebtedness (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,672,957	$ 1,770,054
Net unamortized debt issuance costs	(9,344)	(6,763)
Unamortized fair market value of assumed debt	497	548
Mortgage and other notes payable, net	1,162,617	1,204,581
Unsecured notes payable, net	440,088	420,858
Total Indebtedness	1,664,110	1,763,839
Mortgages
Debt Instrument [Line Items]
Net unamortized debt issuance costs	(4,828)	(6,507)
Unamortized fair market value of assumed debt	497	548
Mortgage and other notes payable, net	1,162,617	1,204,581
Unsecured Debt
Debt Instrument [Line Items]
Net unamortized debt issuance costs	(4,516)	(256)
Unsecured notes payable, net	$ 440,088	420,858
Core Portfolio | Variable Rate Debt | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	1.50%
Core Portfolio | Variable Rate Debt | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	1.90%
Core Portfolio | Unsecured Notes Payable | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	1.55%
Core Portfolio | Mortgages
Debt Instrument [Line Items]
Long-term debt, gross	$ 220,009	228,310
Core Portfolio | Mortgages | Fixed Rate
Debt Instrument [Line Items]
Long-term debt, gross	$ 146,642	$ 147,810
Core Portfolio | Mortgages | Fixed Rate | Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage	3.88%	3.88%
Maturity Date	2024-02
Core Portfolio | Mortgages | Fixed Rate | Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage	5.89%	5.89%
Maturity Date	2035-04
Core Portfolio | Mortgages | Variable Rate - Swapped
Debt Instrument [Line Items]
Long-term debt, gross	$ 73,367	$ 80,500
Core Portfolio | Mortgages | Variable Rate - Swapped | Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage	3.41%	3.41%
Maturity Date	2023-01
Core Portfolio | Mortgages | Variable Rate - Swapped | Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage	4.54%	4.54%
Maturity Date	2028-11
Core Portfolio | Unsecured Debt
Debt Instrument [Line Items]
Long-term debt, gross	$ 400,000	$ 380,000
Core Portfolio | Unsecured Debt | Variable Rate Credit Facility
Debt Instrument [Line Items]
Long-term debt, gross	$ 0	$ 30,000
Core Portfolio | Unsecured Debt | Variable Rate Credit Facility | LIBOR
Debt Instrument [Line Items]
Interest rate, stated percentage		2.55%
Core Portfolio | Unsecured Debt | Variable Rate Unsecured Term Loans - Swapped
Debt Instrument [Line Items]
Maturity Date	2026-06
Long-term debt, gross	$ 400,000	$ 350,000
Core Portfolio | Unsecured Debt | Variable Rate Unsecured Term Loans - Swapped | Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage	3.65%	2.49%
Core Portfolio | Unsecured Debt | Variable Rate Unsecured Term Loans - Swapped | Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage	5.32%	5.02%
Core Portfolio | Line of Credit | Unsecured Line of Credit - Swapped
Debt Instrument [Line Items]
Maturity Date	2025-06
Long-term debt, gross	$ 61,405	$ 138,400
Core Portfolio | Line of Credit | Unsecured Line of Credit - Swapped | Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage	3.65%	2.49%
Core Portfolio | Line of Credit | Unsecured Line of Credit - Swapped | Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage	5.32%	5.02%
Fixed Rate
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,053,715	$ 1,143,152
Variable Rate
Debt Instrument [Line Items]
Long-term debt, gross	619,242	626,902
Fund II | Fund Portfolio
Debt Instrument [Line Items]
Long-term debt, gross	$ 234,110	228,282
Fund II | Fund Portfolio | Variable Rate Debt | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.39%
Fund II | Fund Portfolio | Mortgages
Debt Instrument [Line Items]
Long-term debt, gross	$ 252,771	$ 247,085
Fund II | Fund Portfolio | Mortgages | Variable Rate - Swapped
Debt Instrument [Line Items]
Interest rate, stated percentage	2.88%	2.88%
Maturity Date	2021-11
Long-term debt, gross	$ 18,661	$ 18,803
Fund II | Fund Portfolio | Mortgages | Variable Rate Debt | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	3.00%	3.00%
Maturity Date	2022-03
Fund II | Fund Portfolio | Mortgages | Variable Rate Debt | Prime Rate
Debt Instrument [Line Items]
Basis spread on variable rate	2.00%	2.00%
Maturity Date	2022-08
Fund II | Fund Portfolio | Unsecured Debt | Variable Rate Debt | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.65%	1.65%
Fund II | Fund Portfolio | Unsecured Debt | Unsecured Notes Payable
Debt Instrument [Line Items]
Long-term debt, gross	$ 40,000	$ 40,000
Fund II | Fund Portfolio | Unsecured Debt | Unsecured Notes Payable | LIBOR
Debt Instrument [Line Items]
Maturity Date	2021-09
Fund III | Fund Portfolio | Variable Rate Debt | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	2.75%
Fund III | Fund Portfolio | Variable Rate Debt | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	3.10%
Fund III | Fund Portfolio | Mortgages | Variable Rate Debt
Debt Instrument [Line Items]
Long-term debt, gross	$ 71,308	$ 71,918
Fund III | Fund Portfolio | Mortgages | Variable Rate Debt | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	2.75%	2.75%
Maturity Date	2022-06
Fund III | Fund Portfolio | Mortgages | Variable Rate Debt | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	3.10%	3.10%
Maturity Date	2022-07
Fund IV | Fund Portfolio | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%
Fund IV | Fund Portfolio | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	2.00%
Fund IV | Fund Portfolio | Mortgages
Debt Instrument [Line Items]
Long-term debt, gross	$ 287,756	$ 327,550
Fund IV | Fund Portfolio | Mortgages | Fixed Rate
Debt Instrument [Line Items]
Interest rate, stated percentage	4.50%
Maturity Date	2025-10
Long-term debt, gross	$ 1,120	$ 6,726
Fund IV | Fund Portfolio | Mortgages | Fixed Rate | Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage		3.40%
Fund IV | Fund Portfolio | Mortgages | Fixed Rate | Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage		4.50%
Fund IV | Fund Portfolio | Mortgages | Variable Rate - Swapped
Debt Instrument [Line Items]
Long-term debt, gross	$ 42,549	$ 66,590
Fund IV | Fund Portfolio | Mortgages | Variable Rate - Swapped | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	3.48%	3.48%
Maturity Date	2022-04
Fund IV | Fund Portfolio | Mortgages | Variable Rate - Swapped | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	4.61%	4.61%
Maturity Date	2022-12
Fund IV | Fund Portfolio | Mortgages | Variable Rate Debt
Debt Instrument [Line Items]
Long-term debt, gross	$ 244,087	$ 254,234
Fund IV | Fund Portfolio | Mortgages | Variable Rate Debt | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	1.60%	1.60%
Maturity Date	2021-07
Fund IV | Fund Portfolio | Mortgages | Variable Rate Debt | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	3.40%	3.40%
Maturity Date	2025-10
Fund IV | Fund Portfolio | Unsecured Debt | Term Loan Subscription Facility
Debt Instrument [Line Items]
Long-term debt, gross	$ 0	$ 864
Fund IV | Fund Portfolio | Unsecured Debt | Term Loan Subscription Facility | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.90%	1.90%
Maturity Date	2021-12
Fund V | Fund Portfolio | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	1.50%
Fund V | Fund Portfolio | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	2.20%
Fund V | Fund Portfolio | Mortgages
Debt Instrument [Line Items]
Long-term debt, gross	$ 335,104	$ 335,677
Fund V | Fund Portfolio | Mortgages | Variable Rate - Swapped
Debt Instrument [Line Items]
Long-term debt, gross	$ 304,843	$ 334,323
Fund V | Fund Portfolio | Mortgages | Variable Rate - Swapped | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	2.43%	2.95%
Maturity Date	2021-07
Fund V | Fund Portfolio | Mortgages | Variable Rate - Swapped | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	4.78%	4.78%
Maturity Date	2024-12
Fund V | Fund Portfolio | Mortgages | Variable Rate Debt
Debt Instrument [Line Items]
Long-term debt, gross	$ 30,261	$ 1,354
Fund V | Fund Portfolio | Mortgages | Variable Rate Debt | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	1.50%	1.50%
Maturity Date	2021-07
Fund V | Fund Portfolio | Mortgages | Variable Rate Debt | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	2.20%	2.20%
Maturity Date	2024-12
Fund V | Fund Portfolio | Unsecured Debt | Subscription Line
Debt Instrument [Line Items]
Long-term debt, gross	$ 4,604	$ 250
Fund V | Fund Portfolio | Unsecured Debt | Subscription Line | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.90%	1.60%
Maturity Date	2022-05