Detail of secured and unsecured debt (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2025	Jun. 30, 2024	Feb. 29, 2024	Jul. 31, 2023
Debt Instrument
Effective rate (as a percent)	3.95%
Future principal payments due on secured and unsecured debt
2025	$ 600,034
2026	800,454
2027	350,038
2028	425,041
2029	700,044
Thereafter	10,300,395
Principal	13,176,006
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(85,172)
Total Consolidated	$ 13,090,834
99 Coolidge Avenue | Alexandria
Debt Instrument
Noncontrolling Interest, Ownership Percentage by Parent	75.70%
Secured notes payable
Debt Instrument
Effective rate (as a percent)	7.20%
Future principal payments due on secured and unsecured debt
2025	$ 34
2026	150,454
2027	38
2028	41
2029	44
Thereafter	395
Principal	151,006
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(199)
Total Consolidated	$ 150,807
Secured notes payable maturing on 11/19/26
Debt Instrument
Applicable margin (as a percent)	2.70%
Effective rate (as a percent)	7.20%
Maturity Date	Nov. 19, 2026
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	150,418
2027	0
2028	0
2029	0
Thereafter	0
Principal	150,418
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(199)
Total Consolidated	150,219
Secured notes payable maturing on 11/19/26 | 99 Coolidge Avenue
Debt Instrument
Debt Instrument, Unused Borrowing Capacity, Amount	$ 44,900
Secured Notes Payable Maturing on 7/1/36
Debt Instrument
Stated interest rate (as a percent)	6.50%
Effective rate (as a percent)	6.50%
Maturity Date	Jul. 01, 2036
Future principal payments due on secured and unsecured debt
2025	$ 34
2026	36
2027	38
2028	41
2029	44
Thereafter	395
Principal	588
Unamortized (Deferred Financing Cost), (Discount)/ Premium	0
Total Consolidated	$ 588
Unsecured Debt
Debt Instrument
Effective rate (as a percent)	3.91%
Future principal payments due on secured and unsecured debt
2025	$ 600,000
2026	650,000
2027	350,000
2028	425,000
2029	700,000
Thereafter	10,300,000
Principal	13,025,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(84,973)
Total Consolidated	$ 12,940,027
Unsecured senior line of credit
Debt Instrument
Applicable margin (as a percent)	0.855%	0.875%
Line of Credit Facility, Maximum Borrowing Capacity	$ 5,000,000
Future principal payments due on secured and unsecured debt
Total Consolidated	$ 0
3.45% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	3.45%
Effective rate (as a percent)	3.62%
Maturity Date	Apr. 30, 2025
Future principal payments due on secured and unsecured debt
2025	$ 600,000
2026	0
2027	0
2028	0
2029	0
Thereafter	0
Principal	600,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(74)
Total Consolidated	$ 599,926
4.30% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	4.30%
Effective rate (as a percent)	4.50%
Maturity Date	Jan. 15, 2026
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	300,000
2027	0
2028	0
2029	0
Thereafter	0
Principal	300,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(408)
Total Consolidated	$ 299,592
3.80% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	3.80%
Effective rate (as a percent)	3.96%
Maturity Date	Apr. 15, 2026
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	350,000
2027	0
2028	0
2029	0
Thereafter	0
Principal	350,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(531)
Total Consolidated	$ 349,469
3.95% Unsecured Senior Notes Payable Due in 2027
Debt Instrument
Stated interest rate (as a percent)	3.95%
Effective rate (as a percent)	4.13%
Maturity Date	Jan. 15, 2027
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	350,000
2028	0
2029	0
Thereafter	0
Principal	350,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(940)
Total Consolidated	$ 349,060
3.95% Unsecured Senior Notes Payable Due in 2028
Debt Instrument
Stated interest rate (as a percent)	3.95%
Effective rate (as a percent)	4.07%
Maturity Date	Jan. 15, 2028
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	425,000
2029	0
Thereafter	0
Principal	425,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(1,206)
Total Consolidated	$ 423,794
4.50% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	4.50%
Effective rate (as a percent)	4.60%
Maturity Date	Jul. 30, 2029
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	300,000
Thereafter	0
Principal	300,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(971)
Total Consolidated	$ 299,029
2.75% Unsecured Senior Notes Payable Due 2029
Debt Instrument
Stated interest rate (as a percent)	2.75%
Effective rate (as a percent)	2.87%
Maturity Date	Dec. 15, 2029
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	400,000
Thereafter	0
Principal	400,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(1,962)
Total Consolidated	$ 398,038
4.70% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	4.70%
Effective rate (as a percent)	4.81%
Maturity Date	Jul. 01, 2030
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	0
Thereafter	450,000
Principal	450,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(1,964)
Total Consolidated	$ 448,036
4.90% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	4.90%
Effective rate (as a percent)	5.05%
Maturity Date	Dec. 15, 2030
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	0
Thereafter	700,000
Principal	700,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(4,535)
Total Consolidated	$ 695,465
3.375% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	3.375%
Effective rate (as a percent)	3.48%
Maturity Date	Aug. 15, 2031
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	0
Thereafter	750,000
Principal	750,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(4,188)
Total Consolidated	$ 745,812
2.00% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	2.00%
Effective rate (as a percent)	2.12%
Maturity Date	May 18, 2032
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	0
Thereafter	900,000
Principal	900,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(6,737)
Total Consolidated	$ 893,263
1.875% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	1.875%
Effective rate (as a percent)	1.97%
Maturity Date	Feb. 01, 2033
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	0
Thereafter	1,000,000
Principal	1,000,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(6,892)
Total Consolidated	$ 993,108
2.95% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	2.95%
Effective rate (as a percent)	3.07%
Maturity Date	Mar. 15, 2034
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	0
Thereafter	800,000
Principal	800,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(7,047)
Total Consolidated	$ 792,953
4.75% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	4.75%
Effective rate (as a percent)	4.88%
Maturity Date	Apr. 15, 2035
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	0
Thereafter	500,000
Principal	500,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(4,844)
Total Consolidated	$ 495,156
5.50% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	5.50%
Effective rate (as a percent)	5.66%
Maturity Date	Oct. 01, 2035
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	0
Thereafter	550,000
Principal	550,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(6,777)
Total Consolidated	$ 543,223
5.25% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	5.25%		5.50%
Effective rate (as a percent)	5.38%
Maturity Date	May 15, 2036
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	0
Thereafter	400,000
Principal	400,000		$ 550,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(4,024)
Total Consolidated	$ 395,976
4.85% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	4.85%
Effective rate (as a percent)	4.93%
Maturity Date	Apr. 15, 2049
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	0
Thereafter	300,000
Principal	300,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(2,843)
Total Consolidated	$ 297,157
4.00% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	4.00%
Effective rate (as a percent)	3.91%
Maturity Date	Feb. 01, 2050
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	0
Thereafter	700,000
Principal	700,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	9,951
Total Consolidated	$ 709,951
3.00% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	3.00%
Effective rate (as a percent)	3.08%
Maturity Date	May 18, 2051
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	0
Thereafter	850,000
Principal	850,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(11,130)
Total Consolidated	$ 838,870
3.55% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	3.55%
Effective rate (as a percent)	3.63%
Maturity Date	Mar. 15, 2052
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	0
Thereafter	1,000,000
Principal	1,000,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(13,561)
Total Consolidated	$ 986,439
5.15% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	5.15%
Effective rate (as a percent)	5.26%
Maturity Date	Apr. 15, 2053
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	0
Thereafter	500,000
Principal	500,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(7,537)
Total Consolidated	$ 492,463
5.625% Unsecured Senior Notes Payable
Debt Instrument
Stated interest rate (as a percent)	5.625%
Effective rate (as a percent)	5.71%
Maturity Date	May 15, 2054
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	0
Thereafter	600,000
Principal	600,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(6,636)
Total Consolidated	593,364
Commercial Paper
Debt Instrument
Commercial paper, maximum issuance				$ 2,500,000
Future principal payments due on secured and unsecured debt
Principal	$ 299,900
Commercial Paper | Unsecured senior line of credit
Debt Instrument
Effective rate (as a percent)	4.69%
Maturity Date	Jan. 22, 2030
Future principal payments due on secured and unsecured debt
2025	$ 0
2026	0
2027	0
2028	0
2029	0
Thereafter	300,000
Principal	300,000
Unamortized (Deferred Financing Cost), (Discount)/ Premium	(117)
Total Consolidated	$ 299,883