Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 115,995	$ 102,160	$ 139,687	$ 95,430	$ 330,844	$ 337,830
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	56,051		52,283		165,116	155,924
Amortization of deferred financing costs					8,912	9,230
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes					3,533	3,525
Compensation expense related to stock-based awards					9,987	8,455
Gain on real estate transactions					(1,205)	(30,807)
Distributions from unconsolidated real estate ventures in excess of earnings					4,752	5,235
Changes in operating assets and liabilities:
Other assets					(11,153)	(639)
Accounts payable and accrued expenses					29,310	27,677
Other liabilities					4,370	12,597
Net cash provided by operating activities					544,466	529,027
Cash flows from investing activities:
Acquisition of real estate assets					(287,114)	(327,011)
Development and redevelopment of real estate assets					(34,413)	(45,376)
Proceeds from sale of real estate assets, investments in real estate ventures and other assets					11,254	51,889
Investment in unconsolidated real estate ventures					(33,661)	(52,806)
Return of investment in unconsolidated real estate ventures					3,982	47,964
Issuance of notes receivable					(162,677)	(13,889)
Principal payments received from notes receivable					151,211	25,226
Purchase of equipment and fixtures					(4,959)	(3,026)
Net cash used in investing activities					(356,377)	(317,029)
Cash flows from financing activities:
Proceeds from the sale of common stock, net of offering costs					198,852	33,780
Proceeds from notes payable and revolving lines of credit					1,508,000	973,386
Principal payments on notes payable and revolving lines of credit					(1,503,686)	(787,939)
Principal payments on notes payable to trusts					(30,928)	(21,650)
Deferred financing costs					(2,008)	(7,055)
Repurchase of exchangeable senior notes					0	(80,270)
Net proceeds from exercise of stock options					2,830	1,170
Redemption of Operating Partnership units held by noncontrolling interests					0	(2,558)
Contributions from noncontrolling interests					146	122
Dividends paid on common stock					(341,535)	(315,608)
Distributions to noncontrolling interests					(25,735)	(24,837)
Net cash used in financing activities					(194,064)	(231,459)
Net decrease in cash, cash equivalents, and restricted cash					(5,975)	(19,461)
Cash, cash equivalents, and restricted cash, beginning of the period		72,690		86,044	72,690	86,044	$ 86,044
Cash, cash equivalents, and restricted cash, end of the period	66,715		66,583		66,715	66,583	$ 72,690
Supplemental schedule of cash flow information
Interest paid					136,563	117,627
Income taxes paid					6,197	803
Redemption of Operating Partnership units held by noncontrolling interests for common stock
Common stock and paid-in capital					9,258	955
Establishment of operating lease right of use assets and lease liabilities
Real estate assets - operating lease right-of-use assets	52,413				277,430
Operating lease liabilities					(286,787)
Accounts payable and accrued expenses					9,357
Acquisitions of real estate assets
Real estate assets, net	16,937	223,740	74,694	70,787	249,101	382,765
Notes payable assumed	0	(17,157)	0	0	(17,157)	(87,500)
Investment in unconsolidated real estate ventures	$ 0	$ 2,780	$ 0	$ 489	2,780	(535)
Accrued construction costs and capital expenditures
Acquisition of real estate assets					1,292	275
Accounts payable and accrued expenses					(1,292)	(275)
Conversion of Preferred OP Units to common OP Units
Preferred OP Units					4,374	0
Common OP Units					(4,374)	0
Redemption of Operating Partnership units held by noncontrolling interests for common stock
Redemption of Operating Partnership units held by noncontrolling interests for common stock
Noncontrolling interests in Operating Partnership					(9,258)	(955)
Acquisitions of real estate assets
Acquisitions of real estate assets
Real estate assets, net					19,937	88,842
Value of Operating Partnership units issued					0	(1,877)
Notes payable assumed					(17,157)	(87,500)
Investment in unconsolidated real estate ventures					(2,780)	535
Contribution of Preferred OP Units to unconsolidated real estate venture
Contribution of Preferred OP Units to unconsolidated real estate venture
Investments in unconsolidated real estate ventures					(28,022)	0
Value of Preferred Operating Partnership units issued					$ 28,022	$ 0