Earnings per share (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 8.00% Unsecured Senior Convertible Notes	Dec. 31, 2012 8.00% Unsecured Senior Convertible Notes
Debt Instrument [Line Items]
Stated interest rate (as a percent)					8.00%	8.00%
Earnings per share
Income from continuing operations	$ 32,322,000	$ 20,928,000	$ 61,745,000	$ 47,194,000
Gain on sale of land parcel	772,000	0	772,000	1,864,000
Net income attributable to noncontrolling interests	(980,000)	(851,000)	(1,962,000)	(1,562,000)
Dividends on preferred stock	(6,471,000)	(6,903,000)	(12,942,000)	(14,386,000)
Preferred stock redemption charge	0	0	0	(5,978,000)
Net income attributable to unvested restricted stock awards	(403,000)	(271,000)	(745,000)	(506,000)
Income from continuing operations attributable to Alexandria Real Estate Equities, Inc.'s common stockholders - basic and diluted	25,240,000	12,903,000	46,868,000	26,626,000
Income from discontinued operations, net	243,000	4,713,000	1,057,000	9,358,000
Net income attributable to Alexandria’s common stockholders	$ 25,483,000	$ 17,616,000	$ 47,925,000	$ 35,984,000
Weighted average shares of common stock outstanding - basic	66,973	61,663	65,078	61,586
Dilutive effect of stock options (in shares)	0	1	0	0
Weighted average shares of common stock outstanding - diluted	66,973	61,664	65,078	61,586
Earnings per share attributable to Alexandria Real Estate Equities, Inc.'s common stockholders - basic and diluted:
Continuing operations	$ 0.38	$ 0.21	$ 0.72	$ 0.43
Discontinued operations, net	$ 0.00	$ 0.08	$ 0.02	$ 0.15
Earnings per share – basic and diluted	$ 0.38	$ 0.29	$ 0.74	$ 0.58