Basis of presentation (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011 8.00% Unsecured Convertible Notes	Jul. 31, 2010 8.00% Unsecured Convertible Notes	Jun. 30, 2010 8.00% Unsecured Convertible Notes	Apr. 30, 2009 8.00% Unsecured Convertible Notes	Jun. 30, 2011 3.70% Unsecured Convertible Notes.	Dec. 31, 2010 3.70% Unsecured Convertible Notes.	Apr. 30, 2009 3.70% Unsecured Convertible Notes.	Jan. 31, 2007 3.70% Unsecured Convertible Notes.
Unsecured convertible notes
Stated interest rate (as a percent)	8.00%	8.00%	8.00%	8.00%	8.00%	8.00%	8.00%	8.00%	8.00%	3.70%	3.70%	3.70%	3.70%
Conversion price (in dollars per share)						$ 41.40			$ 41.40	$ 117.36	$ 117.36		$ 117.96
Numerator:
Income (loss) from continuing operations		$ 34,349	$ (12,164)	$ 67,033	$ 16,028
Net income attributable to noncontrolling interests		(938)	(930)	(1,867)	(1,865)
Income (loss) from continuing operations attributable to Alexandria Real Estate Equities, Inc.		33,411	(13,094)	65,166	14,163
Dividends on preferred stock		(7,089)	(7,090)	(14,178)	(14,179)
Income from continuing operations attributable to unvested restricted stock awards		(298)	(149)	(540)	(311)
Income (loss) from continuing operations attributable to Alexandria Real Estate Equities, Inc.'s common stockholders - numerator for basic earnings per share		26,024	(20,333)	50,448	(327)
Income (loss) from continuing operations attributable to Alexandria Real Estate Equities, Inc.'s common stockholders - numerator for diluted earnings per share		$ 26,024	$ (20,333)	$ 50,448	$ (327)
Denominator:
Weighted average shares of common stock outstanding - basic (in shares)		58,500,055	44,870,142	56,734,012	44,348,850
Effect of assumed conversion and dilutive securities:
Dilutive effect of stock options (in shares)		13,067		16,261
Weighted average shares of common stock outstanding - diluted (in shares)		58,513,122	44,870,142	56,750,273	44,348,850
Earnings (loss) per share attributable to Alexandria Real Estate Equities Inc.'s common stockholders - basic:
Continuing operations (in dollars per share)		$ 0.44	$ (0.45)	$ 0.89	$ (0.01)
Discontinued operations, net (in dollars per share)					$ 0.01
Earnings (loss) per share - basic (in dollars per share)		$ 0.44	$ (0.45)	$ 0.89
Earnings (loss) per share attributable to Alexandria Real Estate Equities Inc.'s common stockholders - diluted:
Continuing operations (in dollars per share)		$ 0.44	$ (0.45)	$ 0.89	$ (0.01)
Discontinued operations, net (in dollars per share)					$ 0.01
Earnings (loss) per share - diluted (in dollars per share)		$ 0.44	$ (0.45)	$ 0.89
Dividends declared per common share (in dollars per share)	$ 0.45	$ 0.45	$ 0.35	$ 0.90	$ 0.70