Earnings per share (Details) (USD $)	1 Months Ended	3 Months Ended		6 Months Ended				1 Months Ended		6 Months Ended
	Apr. 30, 2012	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 8.00% Unsecured Senior Convertible Notes	Dec. 31, 2011 8.00% Unsecured Senior Convertible Notes	Apr. 30, 2012 3.70% Unsecured Senior Convertible Notes	Jan. 31, 2012 3.70% Unsecured Senior Convertible Notes	Jun. 30, 2011 3.70% Unsecured Senior Convertible Notes	Jun. 30, 2012 3.70% Unsecured Senior Convertible Notes	Dec. 31, 2011 3.70% Unsecured Senior Convertible Notes
Unsecured convertible notes
Stated interest rate (as a percent)						8.00%	8.00%			3.70%
Conversion price (in dollars per share)										$ 117.36	$ 117.36	$ 117.36
Principal amount of unsecured convertible notes repurchased	$ 1,000,000							$ 1,000,000	$ 83,800,000	$ 96,100,000
Earnings per share
Income from continuing operations		25,435,000	33,974,000	56,211,000	66,287,000
Gain on sale of land parcel				1,864,000
Net income attributable to noncontrolling interests		(851,000)	(938,000)	(1,562,000)	(1,867,000)
Dividends on preferred stock		(6,903,000)	(7,089,000)	(14,386,000)	(14,178,000)
Preferred stock redemption charge				(5,978,000)
Net income attributable to unvested restricted stock awards		(271,000)	(298,000)	(506,000)	(540,000)
Income from continuing operations attributable to Alexandria Real Estate Equities, Inc.'s common stockholders - basic and diluted		17,410,000	25,649,000	35,643,000	49,702,000
Income from discontinued operations, net		206,000	337,000	341,000	649,000
Net income attributable to Alexandria Real Estate Equities, Inc.'s common stockholders		$ 17,616,000	$ 25,986,000	$ 35,984,000	$ 50,351,000
Weighted average shares of common stock outstanding - basic		61,663,367	58,500,055	61,585,587	56,734,012
Dilutive effect of stock options (in shares)		173	13,067	667	16,261
Weighted average shares of common stock outstanding - diluted		61,663,540	58,513,122	61,586,254	56,750,273
Earnings per share attributable to Alexandria Real Estate Equities, Inc.'s common stockholders - basic:
Continuing operations (in dollars per share)		$ 0.29	$ 0.43	$ 0.57	$ 0.88
Discontinued operations, net (in dollars per share)			$ 0.01	$ 0.01	$ 0.01
Basic (in dollars per share)		$ 0.29	$ 0.44	$ 0.58	$ 0.89
Earnings per share attributable to Alexandria Real Estate Equities, Inc.'s common stockholders - diluted:
Continuing operations (in dollars per share)		$ 0.29	$ 0.43	$ 0.57	$ 0.88
Discontinued operations, net (in dollars per share)			$ 0.01	$ 0.01	$ 0.01
Diluted (in dollars per share)		$ 0.29	$ 0.44	$ 0.58	$ 0.89