Earnings per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of basic and diluted EPS
Net income (loss)									$ 404,047	$ 402,793	$ 194,204
Net income attributable to noncontrolling interest									(40,882)	(23,481)	(25,111)
Dividends on preferred stock									(3,204)	(5,060)	(7,666)
Preferred stock redemption charge									(2,580)	(4,240)	(11,279)
Net income attributable to unvested restricted stock awards									(6,386)	(6,029)	(4,753)
Numerator for basic and diluted EPS – net income (loss) attributable to Alexandria Real Estate Equities, Inc.'s common stockholders	$ 199,618	$ (49,773)	$ 76,330	$ 123,598	$ (31,740)	$ 208,940	$ 52,016	$ 132,387	$ 350,995	$ 363,983	$ 145,395
Denominator for basic EPS – weighted-average shares of common stock shares outstanding									112,204,000	103,010,000	91,546,000
Dilutive effect of forward equity sales agreements									320,000	311,000	517,000
Denominator for diluted EPS – weighted-average shares of common stock shares outstanding									112,524,000	103,321,000	92,063,000
Earnings per share attributable to Alexandria's common stockholders – basic and diluted:
Earnings per share - basic (USD per share)	$ 1.75	$ (0.44)	$ 0.68	$ 1.11	$ (0.30)	$ 2.01	$ 0.51	$ 1.33	$ 3.13	$ 3.53	$ 1.59
Earnings per share - diluted (USD per share)	$ 1.74	$ (0.44)	$ 0.68	$ 1.11	$ (0.30)	$ 1.99	$ 0.51	$ 1.32	$ 3.12	$ 3.52	$ 1.58
Series D Convertible Preferred Stock
Class of Stock [Line Items]
Preferred Stock, Shares Outstanding	0				2,573,432				0	2,573,432	3,000,000.0
Preferred Stock, dividend rate (as a percent)									7.00%	7.00%
7.00% Series D Preferred Stock repurchased (in shares)									275,000
Reconciliation of basic and diluted EPS
Preferred stock redemption charge									$ (2,600)	$ (4,200)	$ (5,800)