Consolidated and unconsolidated real estate joint ventures (Details)	1 Months Ended	3 Months Ended			9 Months Ended
	Oct. 25, 2021 USD ($)	Sep. 30, 2021 USD ($) ft²	Jun. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) ft²	Sep. 30, 2020 USD ($)
Schedule of Equity Method Investments
Proceeds from Noncontrolling Interests					$ 629,138,000	$ 64,207,000
Payments to noncontrolling interests					81,926,000	66,095,000
Contributions from and sales of noncontrolling interests		$ 360,551,000		$ 8,561,000	753,971,000	414,025,000
Additional Paid-In Capital
Schedule of Equity Method Investments
Contributions from and sales of noncontrolling interests		95,729,000		15,000	199,644,000	56,026,000
Noncontrolling Interests
Schedule of Equity Method Investments
Payments to noncontrolling interests					81,900,000	64,600,000
Contributions from and sales of noncontrolling interests		$ 264,822,000		$ 8,546,000	$ 554,327,000	$ 357,999,000
75/125 Binney Street
Schedule of Equity Method Investments
Our ownership percentage (in percent)		40.00%			40.00%
225 Binney Street
Schedule of Equity Method Investments
Our ownership percentage (in percent)		30.00%			30.00%
57 Coolidge Avenue
Schedule of Equity Method Investments
Our ownership percentage (in percent)		75.00%			75.00%
409/499 Illinois Street
Schedule of Equity Method Investments
Our ownership percentage (in percent)		60.00%			60.00%
409/499 Illinois Street | Subsequent Event
Schedule of Equity Method Investments
Our ownership percentage (in percent)	25.00%
Proceeds from Noncontrolling Interests	$ 231,000,000
Proceeds from sale of real estate	495,600,000
409/499 Illinois Street | Additional Paid-In Capital | Subsequent Event
Schedule of Equity Method Investments
Contributions from and sales of noncontrolling interests	$ 92,400,000
409/499 Illinois Street | Noncontrolling Interests | Alexandria | Subsequent Event
Schedule of Equity Method Investments
Ownership percentage by noncontrolling owners	75.00%
1500 Owens Street
Schedule of Equity Method Investments
Our ownership percentage (in percent)		50.10%			50.10%
1500 Owens Street | Subsequent Event
Schedule of Equity Method Investments
Our ownership percentage (in percent)	25.00%
Proceeds from Noncontrolling Interests	$ 43,700,000
Proceeds from sale of real estate	130,500,000
1500 Owens Street | Additional Paid-In Capital | Subsequent Event
Schedule of Equity Method Investments
Contributions from and sales of noncontrolling interests	$ 21,300,000
1500 Owens Street | Noncontrolling Interests | Alexandria | Subsequent Event
Schedule of Equity Method Investments
Ownership percentage by noncontrolling owners	75.00%
Alexandria Technology Center - Gateway
Schedule of Equity Method Investments
Our ownership percentage (in percent)		48.10%			48.10%
213 East Grand Avenue
Schedule of Equity Method Investments
Our ownership percentage (in percent)		30.00%			30.00%
Proceeds from Noncontrolling Interests			$ 301,000,000
Proceeds from sale of real estate, per RSF			1,429
213 East Grand Avenue | Additional Paid-In Capital
Schedule of Equity Method Investments
Contributions from and sales of noncontrolling interests			$ 103,700,000
213 East Grand Avenue | Noncontrolling Interests | Alexandria
Schedule of Equity Method Investments
Ownership percentage by noncontrolling owners			70.00%
500 Forbes Boulevard
Schedule of Equity Method Investments
Our ownership percentage (in percent)		10.00%			10.00%
Alexandria Center for Life Science – Millbrae Station
Schedule of Equity Method Investments
Our ownership percentage (in percent)		37.60%			37.60%
Alexandria Point
Schedule of Equity Method Investments
Our ownership percentage (in percent)		55.00%			55.00%
5200 Illumina Way
Schedule of Equity Method Investments
Our ownership percentage (in percent)		51.00%			51.00%
9625 Towne Centre Drive
Schedule of Equity Method Investments
Our ownership percentage (in percent)		50.10%			50.10%
SD Tech by Alexandria
Schedule of Equity Method Investments
Our ownership percentage (in percent)		50.00%			50.00%
Pacific Technology Park
Schedule of Equity Method Investments
Our ownership percentage (in percent)		50.00%			50.00%
Payments to noncontrolling interests		$ 85,800,000
Area of real estate property | ft²		544,352			544,352
Pacific Technology Park | Noncontrolling Interests | Alexandria
Schedule of Equity Method Investments
Ownership percentage by noncontrolling owners		50.00%			50.00%
The Eastlake Life Science Campus by Alexandria
Schedule of Equity Method Investments
Our ownership percentage (in percent)		30.00%			30.00%
400 Dexter Avenue North
Schedule of Equity Method Investments
Our ownership percentage (in percent)		30.00%			30.00%
Proceeds from Noncontrolling Interests		$ 254,800,000
Proceeds from sale of real estate, per RSF		1,255
400 Dexter Avenue North | Additional Paid-In Capital
Schedule of Equity Method Investments
Contributions from and sales of noncontrolling interests		$ 95,500,000
400 Dexter Avenue North | Noncontrolling Interests | Alexandria
Schedule of Equity Method Investments
Ownership percentage by noncontrolling owners		70.00%			70.00%
9444 Waples Street
Schedule of Equity Method Investments
Proceeds from Noncontrolling Interests		$ 11,500,000
Proceeds from sale of real estate, per RSF		$ 260
Area of real estate property | ft²		88,380			88,380
Equity Method Investee | 1655 and 1725 Third Street
Schedule of Equity Method Investments
Our ownership percentage (in percent)		10.00%			10.00%
Equity Method Investee | Menlo Gateway
Schedule of Equity Method Investments
Our ownership percentage (in percent)		49.00%			49.00%
Equity Method Investee | 1401/1413 Research Boulevard
Schedule of Equity Method Investments
Our ownership percentage (in percent)		65.00%			65.00%
Area of real estate property | ft²		90,000			90,000