Debt - Summary of Consolidated Indebtedness (Parenthetical) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,826,271	$ 1,819,738
Interest Rate Caps
Debt Instrument [Line Items]
Long-term debt, gross	107,300	110,500
Total Debt - Variable Rate Debt Fixed with Interest Rate Swap Agreements
Debt Instrument [Line Items]
Long-term debt, gross	798,200	860,400
Core Portfolio | Mortgages
Debt Instrument [Line Items]
Long-term debt, gross	205,397	218,421
Core Portfolio | Interest Rate Swaps
Debt Instrument [Line Items]
Long-term debt, gross	0	0
Fund Portfolio | Mortgages
Debt Instrument [Line Items]
Long-term debt, gross	$ 386,653	388,410
Minimum | Core Portfolio | Variable Rate Debt | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.50%
Minimum | Core Portfolio | Unsecured Notes Payable | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.55%
Minimum | Core Portfolio | Unsecured Line of Credit [Member] | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.40%
Maximum | Core Portfolio | Variable Rate Debt | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.70%
Fund II | Fund Portfolio
Debt Instrument [Line Items]
Long-term debt, gross	$ 256,212	$ 255,978
Fund II | Fund Portfolio | Variable Rate Debt | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	2.75%
Fund II | Fund Portfolio | Variable Rate Debt | LIBOR | Mortgages
Debt Instrument [Line Items]
Basis spread on variable rate	2.75%	2.75%
Fund II | Fund Portfolio | Variable Rate Debt | PRIME
Debt Instrument [Line Items]
Basis spread on variable rate	2.00%
Fund II | Fund Portfolio | Variable Rate Debt | PRIME | Mortgages
Debt Instrument [Line Items]
Basis spread on variable rate	2.00%	2.00%
Fund III | Fund Portfolio
Debt Instrument [Line Items]
Long-term debt, gross	$ 35,970	$ 34,728
Fund III | Fund Portfolio | Variable Rate Debt | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	3.10%
Fund III | Maximum | Fund Portfolio | Variable Rate Debt | LIBOR | Mortgages
Debt Instrument [Line Items]
Basis spread on variable rate	3.10%	2.75%
Fund IV | Fund Portfolio | Mortgages
Debt Instrument [Line Items]
Long-term debt, gross	$ 214,108	$ 246,268
Fund IV | Fund Portfolio | Variable Rate Debt | Mortgages
Debt Instrument [Line Items]
Long-term debt, gross	$ 212,988	$ 221,832
Fund IV | Minimum | Fund Portfolio | Variable Rate Debt | Mortgages
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%
Fund IV | Minimum | Fund Portfolio | Variable Rate Debt | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%
Fund IV | Minimum | Fund Portfolio | Variable Rate Debt | LIBOR | Mortgages
Debt Instrument [Line Items]
Basis spread on variable rate		1.60%
Fund IV | Maximum | Fund Portfolio | Variable Rate Debt | Mortgages
Debt Instrument [Line Items]
Basis spread on variable rate	3.65%
Fund IV | Maximum | Fund Portfolio | Variable Rate Debt | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	3.65%
Fund IV | Maximum | Fund Portfolio | Variable Rate Debt | LIBOR | Mortgages
Debt Instrument [Line Items]
Basis spread on variable rate		3.65%
Fund V | Fund Portfolio | Variable Rate Debt | Mortgages
Debt Instrument [Line Items]
Long-term debt, gross	$ 58,583	$ 58,878
Fund V | Fund Portfolio | Variable Rate Debt | LIBOR | Mortgages
Debt Instrument [Line Items]
Basis spread on variable rate	1.85%
Fund V | Minimum | Fund Portfolio | Variable Rate Debt | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.50%
Fund V | Minimum | Fund Portfolio | Variable Rate Debt | LIBOR | Mortgages
Debt Instrument [Line Items]
Basis spread on variable rate		1.85%
Fund V | Maximum | Fund Portfolio | Variable Rate Debt | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	2.20%
Fund V | Maximum | Fund Portfolio | Variable Rate Debt | LIBOR | Mortgages
Debt Instrument [Line Items]
Basis spread on variable rate	2.76%