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Debt (Summary Of Debt Outstanding) (Details) - USD ($) $ in Thousands		12 Months Ended
	Jul. 25, 2019	Dec. 31, 2019	Aug. 21, 2019	Jun. 07, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Mortgages payable		$ 545,679			$ 474,379
Revolving credit facility		0			0
Notes payable		3,781			279,027
Net unamortized discount and debt issuance costs		(62)			(365)
Senior notes and debentures, net		2,807,134			2,404,279
Capital lease obligations		0			71,519
Total debt and capital lease obligations		3,356,594			3,229,204
Mortgages Payable
Debt Instrument [Line Items]
Principal balance		547,247			475,308
Net unamortized (discount) premium and debt issuance costs		(1,568)			(929)
Notes Payable
Debt Instrument [Line Items]
Notes payable		3,843			279,392
Senior Notes and Debentures
Debt Instrument [Line Items]
Principal balance		2,819,200			2,419,200
Net unamortized (discount) premium and debt issuance costs		(12,066)			(14,921)
Rollingwood Apartments \| Mortgages Payable
Debt Instrument [Line Items]
Principal balance		$ 0			20,331
Interest rate		5.54%
The Shops at Sunset Place \| Mortgages Payable
Debt Instrument [Line Items]
Principal balance		$ 61,987			64,453
Interest rate		5.62%
29th Place \| Mortgages Payable
Debt Instrument [Line Items]
Principal balance		$ 3,878			4,117
Interest rate		5.91%
Sylmar Towne Center \| Mortgages Payable
Debt Instrument [Line Items]
Principal balance		$ 16,630			17,006
Interest rate		5.39%
Plaza Del Sol \| Mortgages Payable
Debt Instrument [Line Items]
Principal balance		$ 8,230			8,409
Interest rate		5.23%
THE AVENUE at White Marsh \| Mortgages Payable
Debt Instrument [Line Items]
Principal balance		$ 52,705			52,705
Interest rate		3.35%
Montrose Crossing \| Mortgages Payable
Debt Instrument [Line Items]
Principal balance		$ 67,492			69,310
Interest rate		4.20%
Azalea \| Mortgages Payable
Debt Instrument [Line Items]
Principal balance		$ 40,000			40,000
Interest rate		3.73%
Bell Gardens \| Mortgages Payable
Debt Instrument [Line Items]
Principal balance		$ 12,677			12,936
Interest rate		4.06%
Plaza El Segundo \| Mortgages Payable
Debt Instrument [Line Items]
Principal balance		$ 125,000			125,000
Interest rate		3.83%
The Grove at Shrewsbury (East) \| Mortgages Payable
Debt Instrument [Line Items]
Principal balance		$ 43,600			43,600
Interest rate		3.77%
Brook 35 \| Mortgages Payable
Debt Instrument [Line Items]
Principal balance		$ 11,500			11,500
Interest rate		4.65%
Hoboken (24 Buildings) \| Mortgages Payable
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.95%
Principal balance		$ 56,450			0
Hoboken (12 Buildings) \| Mortgages Payable
Debt Instrument [Line Items]
Principal balance		24,627			0
Chelsea \| Mortgages Payable
Debt Instrument [Line Items]
Principal balance		$ 5,597			5,941
Interest rate		5.36%
Hoboken (1 Building) \| Mortgages Payable
Debt Instrument [Line Items]
Principal balance		$ 16,874			0
Interest rate		3.75%
Term Loan \| Notes Payable
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.90%
Other Notes Payable		$ 0			275,000
Revolving credit facility
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.775%
Revolving credit facility \| Notes Payable
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.775%
Various \| Notes Payable
Debt Instrument [Line Items]
Interest rate		11.31%
Other Notes Payable		$ 3,843			4,392
2.55% notes \| Senior Notes and Debentures
Debt Instrument [Line Items]
Principal balance		$ 250,000			250,000
Interest rate		2.55%
3.00% notes \| Senior Notes and Debentures
Debt Instrument [Line Items]
Principal balance		$ 250,000			250,000
Interest rate		3.00%
2.75% notes \| Senior Notes and Debentures
Debt Instrument [Line Items]
Principal balance		$ 275,000			275,000
Interest rate		2.75%
3.95% notes \| Senior Notes and Debentures
Debt Instrument [Line Items]
Principal balance		$ 300,000			300,000
Interest rate		3.95%
7.48% debentures \| Senior Notes and Debentures
Debt Instrument [Line Items]
Principal balance		$ 29,200			29,200
Interest rate		7.48%
3.25% Senior notes \| Senior Notes and Debentures
Debt Instrument [Line Items]
Principal balance		$ 475,000			475,000
Interest rate		3.25%
6.82% medium term notes \| Senior Notes and Debentures
Debt Instrument [Line Items]
Principal balance		$ 40,000			40,000
Interest rate		6.82%
3.2% Senior Note
Debt Instrument [Line Items]
Senior notes and debentures, net			$ 100,000	$ 300,000
3.2% Senior Note \| Senior Notes and Debentures
Debt Instrument [Line Items]
Principal balance		$ 400,000			0
Interest rate		3.20%		3.20%
4.50% notes \| Senior Notes and Debentures
Debt Instrument [Line Items]
Principal balance		$ 550,000			550,000
Interest rate		4.50%
3.625% Senior notes \| Senior Notes and Debentures
Debt Instrument [Line Items]
Principal balance		$ 250,000			$ 250,000
Interest rate		3.625%
Minimum \| Hoboken (12 Buildings) \| Mortgages Payable
Debt Instrument [Line Items]
Interest rate		3.91%
Maximum \| Hoboken (12 Buildings) \| Mortgages Payable
Debt Instrument [Line Items]
Interest rate		5.00%