Notes Payable (Summary Of Indebtedness) (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2022	Apr. 01, 2022	Dec. 31, 2021
Unsecured notes payable		$ 3,173,198		$ 3,170,367
Secured notes payable		514,843		0
Total notes payable (2)	[1]	$ 3,688,000		3,170,400
The Funds
Secured notes payable			$ 514,600
Commercial Banks [Member] | 2.88% Term loan, due 2022 [Member]
Debt Instrument, Maturity Date		Sep. 30, 2024
Notes payable, effective interest rate		4.25%
Unsecured notes payable		$ 40,000		39,900
Commercial Banks [Member] | 2.03% Unsecured credit facility [Member]
Notes payable, effective interest rate		2.03%
Senior Unsecured Notes [Member]
Unsecured notes payable		$ 3,133,200		3,130,500
Senior Unsecured Notes [Member] | 3.15% Notes Due 2022 [Member]
Debt Instrument, Maturity Date		Dec. 15, 2022
Notes payable, effective interest rate		3.15%
Unsecured notes payable		$ 349,900		349,300
Senior Unsecured Notes [Member] | 5.07% Notes Due 2023 [Member]
Debt Instrument, Maturity Date		Jun. 15, 2023
Notes payable, effective interest rate		5.07%
Unsecured notes payable		$ 249,700		249,300
Senior Unsecured Notes [Member] | 4.36% Notes Due 2024 [Member]
Debt Instrument, Maturity Date		Jan. 15, 2024
Notes payable, effective interest rate		4.36%
Unsecured notes payable		$ 249,700		249,500
Senior Unsecured Notes [Member] | 3.68% Notes Due 2024 [Member]
Debt Instrument, Maturity Date		Sep. 15, 2024
Notes payable, effective interest rate		3.68%
Unsecured notes payable		$ 249,100		248,800
Senior Unsecured Notes [Member] | 3.74% Notes Due 2028 [Member]
Debt Instrument, Maturity Date		Oct. 15, 2028
Notes payable, effective interest rate		3.74%
Unsecured notes payable		$ 398,100		397,800
Senior Unsecured Notes [Member] | 3.67% Notes Due 2029 [Member]
Debt Instrument, Maturity Date		Jul. 01, 2029
Notes payable, effective interest rate		3.67%
Unsecured notes payable	[2]	$ 595,300		594,900
Senior Unsecured Notes [Member] | 2.91% Notes, due 2030
Debt Instrument, Maturity Date		May 15, 2030
Notes payable, effective interest rate		2.91%
Unsecured notes payable		$ 744,600		744,100
Senior Unsecured Notes [Member] | 3.41% Notes Due 2049 [Member]
Debt Instrument, Maturity Date		Nov. 01, 2049
Notes payable, effective interest rate		3.41%
Unsecured notes payable		$ 296,800		296,800
Secured Debt | 3.78% - 4.04% Conventional Mortgage Notes, due 2026 - 2028
Secured notes payable		$ 291,200		0
Secured Debt | 3.14% Variable Rate Notes, due 2026
Notes payable, effective interest rate		4.58%
Secured notes payable		$ 166,200		0
Secured Debt | 3.44% Variable Rate Construction Note, due 2026
Debt Instrument, Maturity Date		Jun. 20, 2024
Notes payable, effective interest rate		4.95%
Secured notes payable		$ 18,800		0
Secured Debt | 3.87% note, due 2028
Debt Instrument, Maturity Date		Jan. 01, 2028
Notes payable, effective interest rate		3.87%
Secured notes payable		$ 38,600		$ 0
Minimum [Member] | Secured Debt | The Funds
Notes payable, effective interest rate			2.47%
Minimum [Member] | Secured Debt | 3.78% - 4.04% Conventional Mortgage Notes, due 2026 - 2028
Debt Instrument, Maturity Date		Oct. 01, 2026
Notes payable, effective interest rate		3.78%
Minimum [Member] | Secured Debt | 3.14% Variable Rate Notes, due 2026
Debt Instrument, Maturity Date		Apr. 01, 2026
Maximum [Member] | Secured Debt | The Funds
Notes payable, effective interest rate			4.04%
Maximum [Member] | Secured Debt | 3.78% - 4.04% Conventional Mortgage Notes, due 2026 - 2028
Debt Instrument, Maturity Date		Apr. 01, 2028
Notes payable, effective interest rate		4.04%
Maximum [Member] | Secured Debt | 3.14% Variable Rate Notes, due 2026
Debt Instrument, Maturity Date		Oct. 01, 2026

[1] Unamortized debt discounts, debt issuance costs and fair market value adjustments of $18.9 million and $19.6 million are included in notes payable as of September 30, 2022 and December 31, 2021, respectively.

[2] The 2029 Notes have an effective annual interest rate of approximately 3.84% through June 2026, which includes the effect of a settled forward interest rate swap, and approximately 3.28% thereafter, for an all-in average effective rate of approximately 3.67%.