Components of Rental Expense (Components Of Rental Expenses) (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Repairs and maintenance			$ 73,179	$ 67,745	$ 67,996
Utilities			27,729	27,635	25,763
Management fees and costs			24,930	24,024	22,297
Payroll			16,485	16,140	14,922
Insurance			9,036	7,547	7,762
Marketing			7,427	7,935	9,007
Ground rent			4,803	4,697	3,826
Bad debt	[1]		0	4,708	2,591
Other operating	[2]		24,242	12,663	10,726
Total rental expenses			187,831	$ 173,094	$ 164,890
Assembly Square Marketplace
Charge related to the buyout of a lease		$ 11,900	$ 11,900

[1] Collectibility adjustments are now presented as a reduction of rental income rather than rental expense in accordance with our adoption of the new lease standard (see Note 2 for additional disclosure).

[2] Other operating for the year ended December 31, 2019 includes an $11.9 million charge relating to the buyout of a lease at Assembly Square Marketplace.