Condensed consolidating financial information (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Condensed consolidating financial information
Ownership interest in subsidiary (as a percent)	100.00%
Assets
Investments in real estate, net	$ 6,300,027	$ 6,008,440
Cash and cash equivalents	94,904	78,539	73,056	91,232
Restricted cash	44,863	23,332
Tenant receivables	10,124	7,480
Deferred rent	160,914	142,097
Deferred leasing and financing costs, net	152,021	135,550
Investments	107,808	95,777
Other assets	94,356	82,914
Total assets	6,965,017	6,574,129
Liabilities, Noncontrolling Interests, and Equity
Secured notes payable	719,350	724,305
Unsecured senior notes payable	549,794	84,959
Unsecured senior line of credit	413,000	370,000
Unsecured senior bank term loans	1,350,000	1,600,000
Accounts payable, accrued expenses, and tenant security deposits	376,785	325,393
Dividends payable	39,468	36,579
Total liabilities	3,448,397	3,141,236
Redeemable noncontrolling interests	15,610	16,034
Alexandria Real Estate Equities, Inc.'s stockholders' equity	3,455,890	3,374,301
Noncontrolling interests	45,120	42,558
Total equity	3,501,010	3,416,859
Total liabilities, noncontrolling interests, and equity	6,965,017	6,574,129
Alexandria Real Estate Equities, Inc. (Issuer)
Assets
Investments in real estate, net	40,085	46,795
Cash and cash equivalents	50,395	10,608	16,213	48,623
Restricted cash	48	40
Tenant receivables	1	12
Deferred rent	1,693	1,615
Deferred leasing and financing costs, net	33,038	25,364
Investments in and advances to affiliates	5,738,965	5,443,778
Intercompany note receivable	2,244	2,195
Other assets	19,336	18,643
Total assets	5,885,805	5,549,050
Liabilities, Noncontrolling Interests, and Equity
Unsecured senior notes payable	549,794	84,959
Unsecured senior line of credit	413,000	370,000
Unsecured senior bank term loans	1,350,000	1,600,000
Accounts payable, accrued expenses, and tenant security deposits	77,951	83,488
Dividends payable	39,170	36,302
Total liabilities	2,429,915	2,174,749
Alexandria Real Estate Equities, Inc.'s stockholders' equity	3,455,890	3,374,301
Total equity	3,455,890	3,374,301
Total liabilities, noncontrolling interests, and equity	5,885,805	5,549,050
Alexandria Real Estate Equities, L.P. (Guarantor Subsidiary)
Assets
Cash and cash equivalents			110	602
Investments	12,671	13,385
Investments in and advances to affiliates	5,274,333	5,020,525
Total assets	5,287,004	5,033,910
Liabilities, Noncontrolling Interests, and Equity
Alexandria Real Estate Equities, Inc.'s stockholders' equity	5,287,004	5,033,910
Total equity	5,287,004	5,033,910
Total liabilities, noncontrolling interests, and equity	5,287,004	5,033,910
Non-Guarantor Subsidiaries
Assets
Investments in real estate, net	6,259,942	5,961,645
Cash and cash equivalents	44,509	67,931	56,733	42,007
Restricted cash	44,815	23,292
Tenant receivables	10,123	7,468
Deferred rent	159,221	140,482
Deferred leasing and financing costs, net	118,983	110,186
Investments	95,137	82,392
Investments in and advances to affiliates	108,334	105,284
Other assets	75,020	64,271
Total assets	6,916,084	6,562,951
Liabilities, Noncontrolling Interests, and Equity
Secured notes payable	719,350	724,305
Accounts payable, accrued expenses, and tenant security deposits	298,834	241,905
Dividends payable	298	277
Intercompany note payable	2,244	2,195
Total liabilities	1,020,726	968,682
Redeemable noncontrolling interests	15,610	16,034
Alexandria Real Estate Equities, Inc.'s stockholders' equity	5,834,628	5,535,677
Noncontrolling interests	45,120	42,558
Total equity	5,879,748	5,578,235
Total liabilities, noncontrolling interests, and equity	6,916,084	6,562,951
Eliminations
Assets
Investments in and advances to affiliates	(11,121,632)	(10,569,587)
Intercompany note receivable	(2,244)	(2,195)
Total assets	(11,123,876)	(10,571,782)
Liabilities, Noncontrolling Interests, and Equity
Intercompany note payable	(2,244)	(2,195)
Total liabilities	(2,244)	(2,195)
Alexandria Real Estate Equities, Inc.'s stockholders' equity	(11,121,632)	(10,569,587)
Total equity	(11,121,632)	(10,569,587)
Total liabilities, noncontrolling interests, and equity	$ (11,123,876)	$ (10,571,782)