Investments in real estate - Acquisition (Details) $ in Thousands		1 Months Ended	3 Months Ended			9 Months Ended
	Mar. 25, 2021 USD ($)	Oct. 25, 2021 USD ($) ft² property	Sep. 30, 2021 USD ($) ft² property	Jun. 30, 2021 USD ($) ft² property	Mar. 31, 2021 USD ($) ft² property	Sep. 30, 2021 USD ($) ft² property	Sep. 30, 2020 USD ($)	Dec. 31, 2020 ft²
Real Estate
Number of real estate properties acquired | property			27	24	25	27
Payments to acquire real estate | $						$ 3,758,704	$ 1,989,648
Repayments of secured debt | $						17,108	$ 4,741
Deferred purchase price obligation | $			$ 185,200			$ 185,200
704 Quince Orchard Road
Real Estate
Payments to acquire real estate | $	$ 9,400
Area of real estate property								80,032
Repayments of secured debt | $	$ 14,600
704 Quince Orchard Road | Alexandria
Real Estate
Ownership percentage by noncontrolling owners	43.20%
Equity Method Investee | 704 Quince Orchard Road
Real Estate
Our ownership percentage (in percent)								56.80%
Future development
Real Estate
Area of real estate property			3,438,415	4,133,280	374,426	3,438,415
Active development/redevelopment
Real Estate
Area of real estate property			453,869	131,523	849,411	453,869
Operating with future development/redevelopment
Real Estate
Area of real estate property			1,251,105	1,140,916	431,066	1,251,105
Operating property
Real Estate
Acquired in-place leases | $			$ 275,000			$ 275,000
Below-market leases | $			$ 113,100			$ 113,100
Weighted average remaining amortization period, acquired in-place and below-market leases						9 years 1 month 6 days
Area of real estate property			721,490	885,220	1,433,279	721,490
Operating property | Acquired in-place leases
Real Estate
Weighted average remaining amortization period, acquired in-place and below-market leases						8 years 8 months 12 days
Operating property | Below-market leases
Real Estate
Weighted average remaining amortization period, acquired in-place and below-market leases						10 years
Greater Boston
Real Estate
Number of real estate properties acquired | property			4	2	3	4
Payments to acquire real estate | $			$ 192,000	$ 235,000	$ 1,541,326
Greater Boston | Subsequent Event
Real Estate
Payments to acquire real estate | $		$ 25,200
Greater Boston | Future development
Real Estate
Area of real estate property			440,992	1,125,000	305,000	440,992
Greater Boston | Active development/redevelopment
Real Estate
Area of real estate property			453,869	0	640,116	453,869
Greater Boston | Operating with future development/redevelopment
Real Estate
Area of real estate property			173,276	260,867	311,066	173,276
Greater Boston | Operating property
Real Estate
Area of real estate property			0	240,000	692,088	0
San Francisco Bay Area
Real Estate
Number of real estate properties acquired | property			1	7		1
Payments to acquire real estate | $			$ 105,250	$ 217,000
San Francisco Bay Area | Subsequent Event
Real Estate
Number of real estate properties acquired | property		2
Payments to acquire real estate | $		$ 203,800
San Francisco Bay Area | Future development
Real Estate
Area of real estate property			700,000	0		700,000
San Francisco Bay Area | Active development/redevelopment
Real Estate
Area of real estate property			0	0		0
San Francisco Bay Area | Operating with future development/redevelopment
Real Estate
Area of real estate property			223,232	187,043		223,232
San Francisco Bay Area | Operating with future development/redevelopment | Subsequent Event
Real Estate
Area of real estate property		185,228
San Francisco Bay Area | Operating property
Real Estate
Area of real estate property			0	0		0
San Diego
Real Estate
Number of real estate properties acquired | property			14	5		14
Payments to acquire real estate | $			$ 221,234	$ 298,476
San Diego | Future development
Real Estate
Area of real estate property			64,235	887,000		64,235
San Diego | Active development/redevelopment
Real Estate
Area of real estate property			0	0		0
San Diego | Operating with future development/redevelopment
Real Estate
Area of real estate property			440,311	487,023		440,311
San Diego | Operating property
Real Estate
Area of real estate property			413,909	0		413,909
Maryland
Real Estate
Number of real estate properties acquired | property				5
Payments to acquire real estate | $				$ 80,382
Maryland | Future development
Real Estate
Area of real estate property				258,000
Maryland | Active development/redevelopment
Real Estate
Area of real estate property				94,256
Maryland | Operating with future development/redevelopment
Real Estate
Area of real estate property				0
Maryland | Operating property
Real Estate
Area of real estate property				595,381
Research Triangle
Real Estate
Number of real estate properties acquired | property			0			0
Payments to acquire real estate | $			$ 91,000
Research Triangle | Future development
Real Estate
Area of real estate property			1,055,000			1,055,000
Research Triangle | Active development/redevelopment
Real Estate
Area of real estate property			0			0
Research Triangle | Operating with future development/redevelopment
Real Estate
Area of real estate property			0			0
Research Triangle | Operating property
Real Estate
Area of real estate property			0			0
Other markets
Real Estate
Number of real estate properties acquired | property			8	5	22	8
Payments to acquire real estate | $			$ 380,213	$ 247,597	$ 332,424
Other markets | Future development
Real Estate
Area of real estate property			1,178,188	1,863,280	69,426	1,178,188
Other markets | Active development/redevelopment
Real Estate
Area of real estate property			0	37,267	209,295	0
Other markets | Operating with future development/redevelopment
Real Estate
Area of real estate property			414,286	205,983	120,000	414,286
Other markets | Operating property
Real Estate
Area of real estate property			307,581	49,839	741,191	307,581
North America
Real Estate
Number of real estate properties acquired | property			76			76
Payments to acquire real estate | $			$ 989,697	$ 1,078,455	$ 1,873,750	$ 3,941,902
Area of real estate property			38,700,000			38,700,000
North America | Future development
Real Estate
Area of real estate property			7,946,121			7,946,121
North America | Active development/redevelopment
Real Estate
Area of real estate property			1,434,803			1,434,803
North America | Operating with future development/redevelopment
Real Estate
Area of real estate property			2,823,087			2,823,087
North America | Operating property
Real Estate
Area of real estate property			3,039,989			3,039,989