Notes Payable (Narrative) (Details) $ in Thousands		1 Months Ended	3 Months Ended	9 Months Ended
		Aug. 31, 2022 USD ($)	Sep. 30, 2022 USD ($) yr	Sep. 30, 2022 USD ($) yr	Apr. 01, 2022 USD ($)	Dec. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Mar. 31, 2019 USD ($)
Notes Payable	[1]		$ 3,688,000	$ 3,688,000		$ 3,170,400
Unamortized debt discounts and debt issuance costs			18,900	18,900		19,600
Unsecured Debt			$ 3,173,198	$ 3,173,198		3,170,367
Weighted Average Interest Rate	[2]		3.70%	3.70%
Weighted average maturity of indebtedness (including unsecured line of credit) (in years) | yr			6.4	6.4
Secured notes payable			$ 514,843	$ 514,843		0
Debt Instrument, Unamortized Discount (Premium), Net					$ 2,400
Amortization of Debt Discount (Premium)			100	300
The Funds
Secured notes payable					514,600
Letter Of Credit [Member]
Maximum Ability to Issue Letters of Credit Under Unsecured Credit Facility			50,000	50,000
Outstanding balance under credit facility			14,200	14,200
Senior Unsecured Notes [Member]
Unsecured Debt			3,133,200	$ 3,133,200		3,130,500
secured notes payable | The Funds
Secured notes payable					$ 514,600
Secured Debt | The Funds | Minimum [Member]
Notes payable, effective interest rate					2.47%
Secured Debt | The Funds | Maximum [Member]
Notes payable, effective interest rate					4.04%
2.03% Unsecured credit facility [Member]
Maximum term of bid rate loans (days)				180 days
Lesser of amount stated or the amount available under the unsecured credit facility				$ 600,000
Line of Credit Facility, Increase (Decrease), Net		$ 300,000
2.03% Unsecured credit facility [Member] | September 2022 Credit Agreement
Maximum borrowing capacity under unsecured credit facility			$ 1,200,000	$ 1,200,000
2.03% Unsecured credit facility [Member] | March 2019 Credit Agreement
Maximum borrowing capacity under unsecured credit facility								$ 900,000
2.03% Unsecured credit facility [Member] | Commercial Banks [Member]
Notes payable, effective interest rate			2.03%	2.03%
Floating rate notes payable [Member]
Notes Payable			$ 225,000	$ 225,000		39,900	$ 39,900
Weighted Average Interest Rate			4.60%	4.60%			1.90%
2.88% Term loan, due 2022 [Member] | Commercial Banks [Member]
Unsecured Debt			$ 40,000	$ 40,000		$ 39,900
Debt Instrument, Maturity Date				Sep. 30, 2024
Notes payable, effective interest rate			4.25%	4.25%

[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] Includes the effects of the applicable settled forward interest rate swaps.