Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 102,160	$ 95,430
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	54,659	51,749
Amortization of deferred financing costs	3,034	3,021
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	1,162	1,209
Compensation expense related to stock-based awards	2,954	2,726
Distributions from unconsolidated real estate ventures in excess of earnings	1,732	1,501
Changes in operating assets and liabilities:
Other assets	(305)	(737)
Accounts payable and accrued expenses	6,418	10,434
Other liabilities	(2,475)	6,275
Net cash provided by operating activities	169,339	171,608
Cash flows from investing activities:
Acquisition of real estate assets	(212,552)	(76,122)
Development and redevelopment of real estate assets	(15,846)	(11,106)
Proceeds from sale of real estate assets, investments in real estate ventures and other assets	0	753
Investment in unconsolidated real estate ventures	(17,395)	(438)
Return of investment in unconsolidated real estate ventures	0	47,944
Principal payments received from notes receivable	0	9,172
Purchase of equipment and fixtures	(1,182)	(1,131)
Net cash used in investing activities	(246,975)	(30,928)
Cash flows from financing activities:
Proceeds from notes payable and revolving lines of credit	424,000	162,000
Principal payments on notes payable and revolving lines of credit	(225,020)	(168,204)
Principal payments on notes payable to trusts	(30,928)	0
Deferred financing costs	(100)	(117)
Repurchase of exchangeable senior notes	0	(58,464)
Net proceeds from exercise of stock options	1,757	799
Redemption of Operating Partnership units held by noncontrolling interests	0	(2,558)
Contributions from noncontrolling interests	0	120
Dividends paid on common stock	(109,523)	(98,327)
Distributions to noncontrolling interests	(8,412)	(7,909)
Net cash provided by (used in) financing activities	51,774	(172,660)
Net decrease in cash, cash equivalents, and restricted cash	(25,862)	(31,980)
Cash, cash equivalents, and restricted cash, beginning of the period	72,690	86,044	$ 86,044
Cash, cash equivalents, and restricted cash, end of the period	46,828	54,064	$ 72,690
Supplemental schedule of cash flow information
Interest paid	45,165	37,007
Income taxes paid (received)	(177)	492
Redemption of Operating Partnership units held by noncontrolling interests for common stock
Common stock and paid-in capital	3,310	0
Establishment of operating lease right-of-use assets and lease liabilities
Real estate assets - operating lease right-of-use assets	95,506	0
Operating lease liabilities	(104,863)	0
Accounts payable and accrued expenses	9,357	0
Acquisitions of real estate assets
Real estate assets, net	223,740	70,787
Notes payable assumed	(17,157)	0
Accrued construction costs and capital expenditures
Acquisition of real estate assets	780	526
Development and redevelopment of real estate assets	0	1,381
Accounts payable and accrued expenses	(780)	(1,907)
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	(3,310)	0
Acquisitions of real estate assets
Acquisitions of real estate assets
Real estate assets, net	19,937	489
Notes payable assumed	(17,157)	0
Investment in unconsolidated real estate ventures	(2,780)	(489)
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	23,447	0
Value of Preferred Operating Partnership units issued	$ (23,447)	$ 0