Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Cash flow from operating activities:
Net income	$ 90,389	$ 116,678
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	69,397	71,561
Impairment charges	2,974	4,175	$ 4,200
Equity award expense	5,905	5,477
Gain on sale of properties	(3,847)	(23,595)
Distributions from joint ventures and other real estate investments	35,894	28,524
Change in accounts and notes receivable	(1,526)	878
Change in accounts payable and accrued expenses	5,456	2,837
Change in other operating assets and liabilities	(24,787)	(26,299)
Net cash flow provided by operating activities	155,249	155,258
Cash flow from investing activities:
Acquisition of operating real estate	(7,073)	0
Improvements to operating real estate	(54,973)	(51,345)
Improvements to real estate under development	(16,578)	(26,286)
Investments in marketable securities	0	(157)
Proceeds from sale of marketable securities	163	39
Investments in and advances to real estate joint ventures	(5,282)	(5,638)
Reimbursements of investments in and advances to real estate joint ventures	1,914	1,435
Investments in and advances to other real estate investments	(478)	(6,771)
Investment in other financing receivable	0	(48)
Collection of mortgage loans receivable	40	160
Proceeds from sale of operating properties	13,264	72,069
Proceeds from insurance casualty claims	2,450	1,000
Net cash flow used for investing activities	(66,553)	(15,542)
Cash flow from financing activities:
Principal payments on debt, excluding normal amortization of rental property debt	(75,681)	(3,224)
Principal payments on rental property debt	(2,742)	(3,137)
Proceeds from construction loan financing	0	3,300
Proceeds under the unsecured revolving credit facility, net	475,000	0
Financing origination costs	(5,145)	(3)
Payment of early extinguishment of debt charges	0	(771)
Redemption/distribution of noncontrolling interests	(20,926)	(773)
Dividends paid	(127,255)	(132,521)
Proceeds from issuance of stock, net	981	681
Change in other financing liabilities	(5,079)	(3,176)
Net cash flow provided by/(used for) financing activities	239,153	(139,624)
Net change in cash and cash equivalents	327,849	92
Cash and cash equivalents, beginning of the period	123,947	143,581	143,581
Cash and cash equivalents, end of the period	451,796	143,673	$ 123,947
Interest paid during the period including payment of early extinguishment of debt charges of $0 and $771, respectively (net of capitalized interest of $4,364 and $3,137 respectively)	25,383	27,026
Joint Ventures [Member]
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in income	(13,648)	(18,754)
Other Real Estate Investments [Member]
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in income	$ (10,958)	$ (6,224)