Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flow from operating activities:
Net income	$ 258,543	$ 838,507
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	147,449	142,956
Impairment charges	104	3,112
Equity award expense	12,271	11,482
Gain on sale of properties	(28,866)	(5,697)
Gain on marketable securities, net	(85,382)	(521,577)
Gain on sale of cost method investment	0	(190,832)
Distributions from joint ventures and other real estate investments	37,080	55,828
Change in accounts and notes receivable, net	19,127	(31,461)
Change in accounts payable and accrued expenses	5,587	(977)
Change in other operating assets and liabilities, net	(29,346)	(24,348)
Net cash flow provided by operating activities	293,671	237,447
Cash flow from investing activities:
Acquisition of operating real estate	(84,312)	(7,073)
Improvements to operating real estate	(66,342)	(110,826)
Improvements to real estate under development	0	(22,358)
Proceeds from sale of marketable securities	201	906
Proceeds from sale of cost method investment	0	227,521
Investments in and advances to real estate joint ventures	(5,698)	(8,006)
Reimbursements of investments in and advances to real estate joint ventures	3,368	1,737
Investments in and advances to other real estate investments	(55,713)	(1,278)
Reimbursements of investments in and advances to other real estate investments	32,780	0
Investment in other financing receivable	(397)	0
Collection of mortgage loans receivable	93	77
Proceeds from sale of properties	130,138	13,447
Proceeds from insurance casualty claims	0	2,450
Net cash flow (used for)/provided by investing activities	(45,882)	96,597
Cash flow from financing activities:
Principal payments on debt, excluding normal amortization of rental property debt	(136,222)	(88,426)
Principal payments on rental property debt	(5,011)	(5,440)
Proceeds from the unsecured revolving credit facility, net	0	(200,000)
Proceeds from issuance of unsecured term loan	0	590,000
Repayments of unsecured term loan	0	(265,000)
Financing origination costs	0	(6,422)
Contributions from noncontrolling interests	0	109
Redemption/distribution of noncontrolling interests	(3,225)	(22,123)
Dividends paid	(160,092)	(254,716)
Proceeds from issuance of stock, net	1,970	981
Shares repurchased for employee tax withholding on equity awards	(9,225)	(5,313)
Change in tenants' security deposits	890	46
Net cash flow used for financing activities	(310,915)	(256,304)
Net change in cash and cash equivalents	(63,126)	77,740
Cash and cash equivalents, beginning of the period	293,188	123,947
Cash and cash equivalents, end of the period	230,062	201,687
Interest paid during the period (net of capitalized interest of $417 and $8,879, respectively)	96,097	91,502
Joint Ventures [Member]
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in income, net	(34,070)	(23,806)
Other Real Estate Investments [Member]
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in income, net	$ (8,826)	$ (15,740)