CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 10,398,000	$ 114,408,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	194,541,000	198,143,000
Real estate impairment loss	46,000,000
Straight-lining of rental income	(45,671,000)	(43,529,000)
Gain on sale of real estate	(36,845,000)	(133,989,000)
Amortization of stock-based compensation expense	15,245,000	11,692,000
Amortization of above and below-market leases, net	(12,611,000)	(14,164,000)
Amortization of deferred financing costs	8,267,000	8,367,000
Income from unconsolidated joint ventures	(2,931,000)	(19,143,000)
Distributions of earnings from unconsolidated joint ventures	4,910,000	3,380,000
Realized and unrealized gains on marketable securities	(802,000)	(3,198,000)
Loss from unconsolidated real estate funds	268,000	6,053,000
Distributions of earnings from unconsolidated real estate funds	232,000	275,000
Valuation allowance on preferred equity investment		19,588,000
Loss on early extinguishment of debt		7,877,000
Unrealized gain on interest rate swaps		(1,802,000)
Other non-cash adjustments	308,000	(1,104,000)
Changes in operating assets and liabilities:
Accounts and other receivables	877,000	2,260,000
Deferred charges	(20,637,000)	(25,429,000)
Other assets	(31,148,000)	(18,094,000)
Accounts payable and accrued expenses	700,000	(10,710,000)
Other liabilities	3,067,000	1,190,000
Net cash provided by operating activities	134,168,000	102,071,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from sale of real estate	349,013,000	540,333,000
Additions to real estate	(85,621,000)	(59,255,000)
Investments in unconsolidated joint ventures	(25,491,000)	(28,886,000)
Sales of marketable securities	16,352,000	25,855,000
Purchases of marketable securities	(13,192,000)	(28,133,000)
Escrow deposits and loans receivable for Residential Development Fund	(15,680,000)
Contributions of capital to unconsolidated real estate funds	(2,254,000)	(790,000)
Distributions of capital from unconsolidated joint ventures		20,000,000
Acquisitions of real estate		(161,184,000)
Distributions of capital from unconsolidated real estate funds		13,849,000
Net cash provided by investing activities	223,127,000	321,789,000
CASH FLOWS FROM FINANCING ACTIVITIES:
Dividends paid to common stockholders	(70,944,000)	(66,469,000)
Contributions from noncontrolling interests	44,381,000	100,777,000
Proceeds from notes and mortgages payable	16,700,000	991,556,000
Distributions to noncontrolling interests	(10,583,000)	(115,549,000)
Distributions paid to common unitholders	(7,514,000)	(9,100,000)
Debt issuance costs	(6,351,000)	(7,344,000)
Repurchases of common shares	(3,569,000)
Repurchase of shares related to stock compensation agreements and related tax withholdings	(213,000)	(154,000)
Repayments of notes and mortgages payable		(1,044,821,000)
Repayment of borrowings under revolving credit facility		(290,000,000)
Borrowings under revolving credit facility		60,000,000
Transfer tax refund in connection with the acquisition of noncontrolling interests		9,555,000
Settlement of interest rate swap liabilities		(19,425,000)
Loss on early extinguishment of debt		(7,877,000)
Net cash used in financing activities	(38,093,000)	(398,851,000)
Net increase in cash and cash equivalents and restricted cash	319,202,000	25,009,000
Cash and cash equivalents and restricted cash at beginning of period	250,425,000	192,339,000
Cash and cash equivalents and restricted cash at end of period	569,627,000	217,348,000
RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH
Cash and cash equivalents at beginning of period	219,381,000	162,965,000
Restricted cash at beginning of period	31,044,000	29,374,000
Cash and cash equivalents and restricted cash at beginning of period	250,425,000	192,339,000
Cash and cash equivalents at end of period	538,725,000	185,028,000
Restricted cash at end of period	30,902,000	32,320,000
Cash and cash equivalents and restricted cash at end of period	569,627,000	217,348,000
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash payments for interest	101,989,000	106,731,000
Cash payments for income taxes, net of refunds	1,541,000	5,042,000
NON-CASH TRANSACTIONS:
Dividends and distributions declared but not yet paid	26,596,000	25,211,000
Additions to real estate included in accounts payable and accrued expenses	32,790,000	10,986,000
Basis adjustment to investment in unconsolidated joint ventures upon adoption of ASU 2017-05	7,086,000
Write-off of fully amortized and/or depreciated assets	3,141,000	5,958,000
Common shares issued upon redemption of common units	3,461,000	166,524,000
Change in value of interest rate swaps	$ (23,738,000)	(729,000)
Consolidation of real estate		102,512,000
Assumption of notes and mortgages payable		$ 228,000,000