Condensed consolidating financial information Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2015	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Activities
Net income			$ 146,114	$ 106,778	$ 140,249
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and amortization			261,289	224,096	190,778
Loss on early extinguishment of debt			189	525	1,992
(Gain) loss on sale of real estate			(12,426)	(1,838)	121
Impairment of real estate		$ 51,675	23,250	51,675	0
Gain on sales of real estate - land parcels			0	(6,403)	(4,824)
Equity in earnings of unconsolidated joint ventures			(1,651)	(554)	0
Distributions of earnings from unconsolidated joint ventures			873	549	0
Amortization of loan fees and costs			11,003	10,909	9,936
Amortization of debt premiums/discounts			(372)	117	529
Amortization of acquired above and below market leases			(6,118)	(2,845)	(3,316)
Deferred rent			(47,483)	(44,726)	(27,935)
Stock compensation expense			17,512	13,996	15,552
Equity in earnings of affiliates			0	0	0
Investment gains			(35,035)	(11,613)	(7,050)
Investment losses			16,093	9,287	1,480
Changes in operating assets and liabilities:
Restricted cash			60	4,141	899
Tenant receivables			7	(673)	(1,519)
Deferred leasing costs			(65,415)	(38,282)	(54,825)
Other assets			(9,079)	(7,466)	(6,298)
Intercompany receivables and payables					0
Accounts payable, accrued expenses, and tenant security deposits			43,800	26,652	56,958
Net cash provided by operating activities			342,611	334,325	312,727
Investing Activities
Proceeds from sales of real estate			129,799	81,580	153,968
Additions to real estate			(564,206)	(497,773)	(593,389)
Purchase of real estate			(248,933)	(127,887)	(122,069)
Deposits for investing activities			(5,501)	(10,282)	0
Change in restricted cash related to construction projects			0	1,665	7,655
Investment in unconsolidated joint venture			(9,027)	(70,758)	(17,987)
Payments to Acquire Interest in Subsidiaries and Affiliates			0	0	0
Additions to investments			(95,945)	(60,230)	(36,078)
Sales of investments			67,136	18,973	16,525
Repayment of notes receivable			4,282	29,883	0
Net cash used in investing activities			(722,395)	(634,829)	(591,375)
Financing Activities
Borrowings from secured notes payable			169,754	126,215	28,489
Repayments of borrowings from secured notes payable			(89,815)	(231,051)	(36,219)
Proceeds from issuance of unsecured senior notes payable			298,872	698,908	498,561
Principal borrowings from unsecured senior line of credit			2,145,000	1,168,000	729,000
Repayments of borrowings from unsecured senior line of credit			(2,298,000)	(1,068,000)	(1,091,000)
Repayment of unsecured senior bank term loan			(25,000)	(125,000)	(250,000)
Repayments of Convertible Debt			0	0	384
Redemption of Series D Cumulative Convertible Preferred Stock			0	(14,414)	0
Transfers Due to (due from) Parent Entity			0	0	0
Change in restricted cash related to financings			3,842	(1,409)	2,546
Loan fees and costs paid			(10,584)	(8,099)	(19,928)
Proceeds from common stock offerings			78,463	0	534,469
Dividends paid on common stock			(218,104)	(202,386)	(169,076)
Dividends paid on preferred stock			(24,986)	(25,885)	(25,885)
Contributions by noncontrolling interests			453,750	19,410	0
Distributions to noncontrolling interests			(64,066)	(4,977)	(3,003)
Net cash provided by financing activities			419,126	331,312	197,570
Effect of foreign exchange rate changes on cash and cash equivalents			(255)	(2,493)	(2,197)
Net (decrease) increase in cash and cash equivalents			39,087	28,315	(83,275)
Cash and cash equivalents at beginning of period	$ 86,011	57,696	86,011	57,696	140,971
Cash and cash equivalents at end of period			125,098	86,011	57,696
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest, net of interest capitalized			93,856	57,966	59,857
Non-Cash Investing Activities
Note receivable issued in connection with sale of real estate	0			2,000	38,820
Changes in accrued construction			(10,070)	29,846	(21,310)
Assumption of secured notes payable in connection with purchase of properties			(82,000)	(48,329)	0
Payments to Acquire Additional Interest in Subsidiaries			(51,092)	0	0
Alexandria Real Estate Equities, Inc. (Issuer)
Operating Activities
Net income			144,217	101,574	136,217
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and amortization			5,986	5,748	5,907
Loss on early extinguishment of debt			189	525	1,992
(Gain) loss on sale of real estate			0	0	0
Impairment of real estate			0	0
Gain on sales of real estate - land parcels			0	0	0
Equity in earnings of unconsolidated joint ventures			0	0
Distributions of earnings from unconsolidated joint ventures			0	0
Amortization of loan fees and costs			7,605	7,355	6,914
Amortization of debt premiums/discounts			337	232	111
Amortization of acquired above and below market leases			0	0	0
Deferred rent			0	0	(82)
Stock compensation expense			17,512	13,996	15,552
Equity in earnings of affiliates			(268,156)	(199,800)	(220,158)
Investment gains			0	0	0
Investment losses			0	0	0
Changes in operating assets and liabilities:
Restricted cash			(24)	(12)	(2)
Tenant receivables			0	0	0
Deferred leasing costs			0	17	(37)
Other assets			(10,797)	(7,785)	(5,606)
Intercompany receivables and payables					3,021
Accounts payable, accrued expenses, and tenant security deposits			28,078	25,877	(13,485)
Net cash provided by operating activities			(75,053)	(52,273)	(69,656)
Investing Activities
Proceeds from sales of real estate			0	0	10,796
Additions to real estate			0	(65)	0
Purchase of real estate			0	0	0
Deposits for investing activities			0	0
Change in restricted cash related to construction projects				0	0
Investment in unconsolidated joint venture			0	0	0
Payments to Acquire Interest in Subsidiaries and Affiliates			(51,070)	(334,764)	(236,218)
Additions to investments			0	0	0
Sales of investments			0	0	0
Repayment of notes receivable			0	0
Net cash used in investing activities			(51,070)	(334,829)	(225,422)
Financing Activities
Borrowings from secured notes payable			0	0	0
Repayments of borrowings from secured notes payable			0	0	0
Proceeds from issuance of unsecured senior notes payable			298,872	698,908	498,561
Principal borrowings from unsecured senior line of credit			2,145,000	1,168,000	729,000
Repayments of borrowings from unsecured senior line of credit			(2,298,000)	(1,068,000)	(1,091,000)
Repayment of unsecured senior bank term loan			(25,000)	(125,000)	(250,000)
Repayments of Convertible Debt					384
Redemption of Series D Cumulative Convertible Preferred Stock				(14,414)
Transfers Due to (due from) Parent Entity			155,194	103	0
Change in restricted cash related to financings			0	0	(1)
Loan fees and costs paid			(5,825)	(6,523)	(14,383)
Proceeds from common stock offerings			78,463		534,469
Dividends paid on common stock			(218,104)	(202,386)	(169,076)
Dividends paid on preferred stock			(24,986)	(25,885)	(25,885)
Contributions by noncontrolling interests			0	0
Distributions to noncontrolling interests			0	0	0
Net cash provided by financing activities			105,614	424,803	211,301
Effect of foreign exchange rate changes on cash and cash equivalents			0	0	0
Net (decrease) increase in cash and cash equivalents			(20,509)	37,701	(83,777)
Cash and cash equivalents at beginning of period	52,491	14,790	52,491	14,790	98,567
Cash and cash equivalents at end of period			31,982	52,491	14,790
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest, net of interest capitalized			70,946	39,871	37,073
Non-Cash Investing Activities
Note receivable issued in connection with sale of real estate				0	29,820
Changes in accrued construction			0	0	0
Assumption of secured notes payable in connection with purchase of properties			0	0
Payments to Acquire Additional Interest in Subsidiaries			0
Alexandria Real Estate Equities, L.P. (Guarantor Subsidiary)
Operating Activities
Net income			238,486	184,992	205,919
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and amortization			0	0	0
Loss on early extinguishment of debt			0	0	0
(Gain) loss on sale of real estate			0	0	0
Impairment of real estate			0	0
Gain on sales of real estate - land parcels			0	0	0
Equity in earnings of unconsolidated joint ventures			0	0
Distributions of earnings from unconsolidated joint ventures			0	0
Amortization of loan fees and costs			0	0	0
Amortization of debt premiums/discounts			0	0	0
Amortization of acquired above and below market leases			0	0	0
Deferred rent			0	0	0
Stock compensation expense			0	0	0
Equity in earnings of affiliates			(238,691)	(188,269)	(205,993)
Investment gains			0	0	(3)
Investment losses			346	3,047	78
Changes in operating assets and liabilities:
Restricted cash			0	0	0
Tenant receivables			0	0	0
Deferred leasing costs			0	0	0
Other assets			0	0	0
Intercompany receivables and payables					0
Accounts payable, accrued expenses, and tenant security deposits			8	0	0
Net cash provided by operating activities			149	(230)	1
Investing Activities
Proceeds from sales of real estate			0	0	0
Additions to real estate			0	0	0
Purchase of real estate			0	0	0
Deposits for investing activities			0	0
Change in restricted cash related to construction projects				0	0
Investment in unconsolidated joint venture			0	0	0
Payments to Acquire Interest in Subsidiaries and Affiliates			44,687	(251,358)	(276,022)
Additions to investments			0	(150)	0
Sales of investments			6	1,052	1,018
Repayment of notes receivable			0	0
Net cash used in investing activities			44,693	(250,456)	(275,004)
Financing Activities
Borrowings from secured notes payable			0	0	0
Repayments of borrowings from secured notes payable			0	0	0
Proceeds from issuance of unsecured senior notes payable				0	0
Principal borrowings from unsecured senior line of credit			0	0	0
Repayments of borrowings from unsecured senior line of credit			0	0	0
Repayment of unsecured senior bank term loan			0	0	0
Repayments of Convertible Debt					0
Redemption of Series D Cumulative Convertible Preferred Stock				0
Transfers Due to (due from) Parent Entity			(44,905)	250,749	273,089
Change in restricted cash related to financings			0	0	0
Loan fees and costs paid			0	0	0
Proceeds from common stock offerings			0		0
Dividends paid on common stock			0	0	0
Dividends paid on preferred stock			0	0	0
Contributions by noncontrolling interests			0	0
Distributions to noncontrolling interests			0	0	0
Net cash provided by financing activities			(44,905)	250,749	273,089
Effect of foreign exchange rate changes on cash and cash equivalents			0	0	0
Net (decrease) increase in cash and cash equivalents			(63)	63	(1,914)
Cash and cash equivalents at beginning of period	63	0	63	0	1,914
Cash and cash equivalents at end of period			0	63	0
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest, net of interest capitalized			0	0	0
Non-Cash Investing Activities
Note receivable issued in connection with sale of real estate				0	0
Changes in accrued construction			0	0	0
Assumption of secured notes payable in connection with purchase of properties			0	0
Payments to Acquire Additional Interest in Subsidiaries			0
Combined Non- Guarantor Subsidiaries
Operating Activities
Net income			274,962	211,946	228,331
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and amortization			255,303	218,348	184,871
Loss on early extinguishment of debt			0	0	0
(Gain) loss on sale of real estate			(12,426)	(1,838)	121
Impairment of real estate			23,250	51,675
Gain on sales of real estate - land parcels			0	(6,403)	(4,824)
Equity in earnings of unconsolidated joint ventures			(1,651)	(554)
Distributions of earnings from unconsolidated joint ventures			873	549
Amortization of loan fees and costs			3,398	3,554	3,022
Amortization of debt premiums/discounts			(709)	(115)	418
Amortization of acquired above and below market leases			(6,118)	(2,845)	(3,316)
Deferred rent			(47,483)	(44,726)	(27,853)
Stock compensation expense			0	0	0
Equity in earnings of affiliates			(4,704)	(3,665)	(4,067)
Investment gains			(35,035)	(11,613)	(7,047)
Investment losses			15,747	6,240	1,402
Changes in operating assets and liabilities:
Restricted cash			84	4,153	901
Tenant receivables			7	(673)	(1,519)
Deferred leasing costs			(65,415)	(38,299)	(54,788)
Other assets			1,718	319	(692)
Intercompany receivables and payables					(3,021)
Accounts payable, accrued expenses, and tenant security deposits			15,714	775	70,443
Net cash provided by operating activities			417,515	386,828	382,382
Investing Activities
Proceeds from sales of real estate			129,799	81,580	143,172
Additions to real estate			(564,206)	(497,708)	(593,389)
Purchase of real estate			(248,933)	(127,887)	(122,069)
Deposits for investing activities			(5,501)	(10,282)
Change in restricted cash related to construction projects				1,665	7,655
Investment in unconsolidated joint venture			(9,027)	(70,758)	(17,987)
Payments to Acquire Interest in Subsidiaries and Affiliates			1,374	(13,441)	(13,445)
Additions to investments			(95,945)	(60,080)	(36,078)
Sales of investments			67,130	17,921	15,507
Repayment of notes receivable			4,282	29,883
Net cash used in investing activities			(721,027)	(649,107)	(616,634)
Financing Activities
Borrowings from secured notes payable			169,754	126,215	28,489
Repayments of borrowings from secured notes payable			(89,815)	(231,051)	(36,219)
Proceeds from issuance of unsecured senior notes payable				0	0
Principal borrowings from unsecured senior line of credit			0	0	0
Repayments of borrowings from unsecured senior line of credit			0	0	0
Repayment of unsecured senior bank term loan			0	0	0
Repayments of Convertible Debt					0
Redemption of Series D Cumulative Convertible Preferred Stock				0
Transfers Due to (due from) Parent Entity			(105,280)	348,711	252,596
Change in restricted cash related to financings			3,842	(1,409)	2,547
Loan fees and costs paid			(4,759)	(1,576)	(5,545)
Proceeds from common stock offerings			0		0
Dividends paid on common stock			0	0	0
Dividends paid on preferred stock			0	0	0
Contributions by noncontrolling interests			453,750	19,410
Distributions to noncontrolling interests			(64,066)	(4,977)	(3,003)
Net cash provided by financing activities			363,426	255,323	238,865
Effect of foreign exchange rate changes on cash and cash equivalents			(255)	(2,493)	(2,197)
Net (decrease) increase in cash and cash equivalents			59,659	(9,449)	2,416
Cash and cash equivalents at beginning of period	33,457	42,906	33,457	42,906	40,490
Cash and cash equivalents at end of period			93,116	33,457	42,906
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest, net of interest capitalized			22,910	18,095	22,784
Non-Cash Investing Activities
Note receivable issued in connection with sale of real estate				2,000	9,000
Changes in accrued construction			(10,070)	29,846	(21,310)
Assumption of secured notes payable in connection with purchase of properties			(82,000)	(48,329)
Payments to Acquire Additional Interest in Subsidiaries			(51,092)
Eliminations
Operating Activities
Net income			(511,551)	(391,734)	(430,218)
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and amortization			0	0	0
Loss on early extinguishment of debt			0	0	0
(Gain) loss on sale of real estate			0	0	0
Impairment of real estate			0	0
Gain on sales of real estate - land parcels			0	0	0
Equity in earnings of unconsolidated joint ventures			0	0
Distributions of earnings from unconsolidated joint ventures			0	0
Amortization of loan fees and costs			0	0	0
Amortization of debt premiums/discounts			0	0	0
Amortization of acquired above and below market leases			0	0	0
Deferred rent			0	0	0
Stock compensation expense			0	0	0
Equity in earnings of affiliates			511,551	391,734	430,218
Investment gains			0	0	0
Investment losses			0	0	0
Changes in operating assets and liabilities:
Restricted cash			0	0	0
Tenant receivables			0	0	0
Deferred leasing costs			0	0	0
Other assets			0	0	0
Intercompany receivables and payables					0
Accounts payable, accrued expenses, and tenant security deposits			0	0	0
Net cash provided by operating activities			0	0	0
Investing Activities
Proceeds from sales of real estate			0	0	0
Additions to real estate			0	0	0
Purchase of real estate			0	0	0
Deposits for investing activities			0	0
Change in restricted cash related to construction projects				0	0
Investment in unconsolidated joint venture			0	0	0
Payments to Acquire Interest in Subsidiaries and Affiliates			5,009	599,563	525,685
Additions to investments			0	0	0
Sales of investments			0	0	0
Repayment of notes receivable			0	0
Net cash used in investing activities			5,009	599,563	525,685
Financing Activities
Borrowings from secured notes payable			0	0	0
Repayments of borrowings from secured notes payable			0	0	0
Proceeds from issuance of unsecured senior notes payable			0	0	0
Principal borrowings from unsecured senior line of credit			0	0	0
Repayments of borrowings from unsecured senior line of credit			0	0	0
Repayment of unsecured senior bank term loan			0	0	0
Repayments of Convertible Debt					0
Redemption of Series D Cumulative Convertible Preferred Stock				0
Transfers Due to (due from) Parent Entity			(5,009)	(599,563)	(525,685)
Change in restricted cash related to financings			0	0	0
Loan fees and costs paid			0	0	0
Proceeds from common stock offerings			0		0
Dividends paid on common stock			0	0	0
Dividends paid on preferred stock			0	0	0
Contributions by noncontrolling interests			0	0
Distributions to noncontrolling interests			0	0	0
Net cash provided by financing activities			(5,009)	(599,563)	(525,685)
Effect of foreign exchange rate changes on cash and cash equivalents			0	0	0
Net (decrease) increase in cash and cash equivalents			0	0	0
Cash and cash equivalents at beginning of period	$ 0	$ 0	0	0	0
Cash and cash equivalents at end of period			0	0	0
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest, net of interest capitalized			0	0	0
Non-Cash Investing Activities
Note receivable issued in connection with sale of real estate				0	0
Changes in accrued construction			0	0	$ 0
Assumption of secured notes payable in connection with purchase of properties			0	$ 0
Payments to Acquire Additional Interest in Subsidiaries			$ 0