CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash Flows from Operating Activities:
Net income	$ 1,884,000	$ 5,226,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	58,305,000	59,117,000
Straight-lining of rental revenue	(7,282,000)	(10,611,000)
Amortization of stock-based compensation expense	5,486,000	5,397,000
Loss from unconsolidated joint ventures	5,316,000	4,221,000
Amortization of deferred financing costs	2,319,000	2,318,000
Distributions of earnings from unconsolidated real estate funds	137,000	189,000
Distributions of earnings from unconsolidated joint ventures		935,000
Realized and unrealized (gains) losses on marketable securities	(858,000)	2,199,000
Amortization of above and below-market leases, net	(855,000)	(1,508,000)
Income from unconsolidated real estate funds	(180,000)	(52,000)
Other non-cash adjustments	735,000	36,000
Changes in operating assets and liabilities:
Accounts and other receivables	4,850,000	1,405,000
Deferred charges	(159,000)	(4,389,000)
Other assets	(29,311,000)	(28,083,000)
Accounts payable and accrued expenses	16,997,000	(7,019,000)
Other liabilities	946,000	(2,421,000)
Net cash provided by operating activities	58,330,000	26,960,000
Cash Flows from Investing Activities:
Additions to real estate	(19,339,000)	(30,460,000)
Purchases of marketable securities	(9,562,000)	(8,187,000)
Sales of marketable securities	2,557,000	4,780,000
Repayment of amounts due from affiliates		36,918,000
Contributions of capital to unconsolidated real estate funds		(2,936,000)
Net cash (used in) provided by investing activities	(26,344,000)	115,000
Cash Flows from Financing Activities:
Dividends paid to common stockholders	(15,317,000)	(22,743,000)
Proceeds from notes and mortgages payable	12,430,000	3,073,000
Distributions to noncontrolling interests	(4,625,000)	(3,172,000)
Distributions paid to common unitholders	(1,479,000)	(2,512,000)
Contributions from noncontrolling interests	121,000	8,055,000
Repurchase of shares related to stock compensation agreements and related tax withholdings	(200,000)	(309,000)
Borrowings under revolving credit facility		163,082,000
Repurchases of common shares		(97,013,000)
Repayment of note payable issued in connection with the acquisition of noncontrolling interest in unconsolidated real estate fund		(8,771,000)
Net cash (used in) provided by financing activities	(9,070,000)	39,690,000
Net increase in cash and cash equivalents and restricted cash	22,916,000	66,765,000
Cash and cash equivalents and restricted cash at beginning of period	465,324,000	331,487,000
Cash and cash equivalents and restricted cash at end of period	488,240,000	398,252,000
Reconciliation of Cash and Cash Equivalents and Restricted Cash:
Cash and cash equivalents at beginning of period	434,530,000	306,215,000
Restricted cash at beginning of period	30,794,000	25,272,000
Cash and cash equivalents and restricted cash at beginning of period	465,324,000	331,487,000
Cash and cash equivalents at end of period	464,652,000	377,689,000
Restricted cash at end of period	23,588,000	20,563,000
Cash and cash equivalents and restricted cash at end of period	488,240,000	398,252,000
Supplemental Disclosure of Cash Flow Information:
Cash payments for interest	32,401,000	34,565,000
Cash payments for income taxes, net of refunds	24,000	575,000
Non-Cash Transactions:
Dividends and distributions declared but not yet paid	16,889,000	24,342,000
Additions to real estate included in accounts payable and accrued expenses	6,223,000	14,878,000
Write-off of fully amortized and/or depreciated assets	$ 2,142,000	3,794,000
Common shares issued upon redemption of common units		$ 85,311,000