Earnings per share (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Earnings per share
Income from continuing operations																	$ 99,142,000		$ 134,525,000		$ 94,848,000
Gain on sales of real estate - land parcels																	6,403,000		4,824,000		1,864,000
Net income attributable to noncontrolling interests																	(5,204,000)		(4,032,000)		(3,402,000)
Dividends on preferred stock																	(25,698,000)		(25,885,000)		(27,328,000)
Preferred stock redemption charge																	(1,989,000)		0		(5,978,000)
Net income attributable to unvested restricted stock awards																	1,774,000		1,581,000		1,190,000
Income from continuing operations attributable to Alexandria Real Estate Equities, Inc.'s common stockholders - basic and diluted																	70,880,000		107,851,000		58,814,000
(Loss) income from discontinued operations, net																	1,233,000	[1]	900,000	[1]	8,816,000	[1]
Net income attributable to Alexandria’s common stockholders																	72,113,000		108,751,000		67,630,000
Weighted average shares of common stock outstanding – basic and diluted																	71,170		68,038		62,160
Earnings per share attributable to Alexandria Real Estate Equities, Inc.'s common stockholders - basic and diluted:
Continuing operations																	$ 0.99		$ 1.59		$ 0.95
Discontinued operations																	$ 0.02		$ 0.01		$ 0.14
Earnings per share – basic and diluted	$ (0.23)	[2],[3]	$ 0.39	[2]	$ 0.39	[2]	$ 0.46	[2]	$ 0.51	[2]	$ 0.35	[2]	$ 0.38	[2]	$ 0.36	[2]	$ 1.01		$ 1.60		$ 1.09
Convertible Notes Outstanding [Member]
Debt Instrument [Line Items]
Convertible Notes Payable	$ 0																$ 0

[1] Income from discontinued operations includes the results of operations of three properties that were disposed of during the year ended December 31, 2014, and the results of one property which was classified as “held for sale” prior to adoption of the new ASU and included as discontinued operations as of December 31, 2014, as well as the results of operations (prior to disposition) and gain (loss) on sale of real estate attributable to 16 properties sold during the period from January 1, 2012, to December 31, 2014.

[2] (1)Quarterly earnings per common share amounts may not total to the annual amounts due to rounding and due to the increase in the weighted average shares of common stock outstanding.

[3] (2)Results for the fourth quarter of 2014 include an aggregate net loss of $46.2 million, or $0.65 per share, related to impairments of real estate and a preferred stock redemption charge, partially offset by gains on sales of real estate. See further discussion of impairments of real estate and gains on real estate in Note 3 – “Investments in Real Estate.