Condensed consolidating financial information Cash Flows (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended			9 Months Ended
	Dec. 31, 2014	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Operating Activities
Net income		$ 39,699		$ 35,943	$ 103,137	$ 112,808
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		67,953		58,388	189,044	166,123
Loss on early extinguishment of debt		0		525	189	525
Impairment of real estate	$ 16,600	0		0	14,510	0
Equity in earnings of unconsolidated joint ventures		(710)		0	(1,825)	0
Distributions of earnings from unconsolidated joint ventures					740	0
Gain on sale of land parcel		0		(8)	0	(805)
Amortization of loan fees					8,348	8,090
Amortization of debt premiums/discounts					(282)	100
Amortization of acquired below-market leases					(5,121)	(2,191)
Deferred rent					(34,421)	(35,511)
Stock compensation expense					12,922	9,372
Equity in earnings of affiliates		0		0	0	0
Investment gains		(8,658)		(3,256)	(22,368)	(9,481)
Investment losses		3,280		3,485	11,157	8,725
Changes in operating assets and liabilities:
Restricted cash					24	0
Tenant receivables					380	(939)
Deferred leasing costs					(47,725)	(25,910)
Other assets					(13,721)	(12,228)
Accounts payable, accrued expenses, and tenant security deposits					31,423	36,446
Net cash provided by operating activities					246,411	255,124
Investing Activities
Proceeds from sale of properties					92,455	28,378
Additions to real estate					(362,215)	(345,074)
Purchase of real estate					(248,933)	(97,785)
Deposits for investing activities					(6,707)	(7,292)
Change in restricted cash related to construction projects					0	6,694
Investment in unconsolidated real estate joint ventures					(7,979)	(67,525)
Investments in subsidiaries					0	0
Additions to investments					(67,965)	(35,484)
Sales of investments					39,590	13,883
Repayment of notes receivable					4,264	29,866
Net cash used in investing activities					(557,490)	(474,339)
Financing Activities
Borrowings from secured notes payable					47,375	108,626
Repayments of borrowings from secured notes payable					(12,217)	(228,909)
Proceeds from issuance of unsecured senior notes payable					0	698,908
Principal borrowings from unsecured senior line of credit					1,432,000	890,000
Repayments of borrowings from unsecured senior line of credit					(893,000)	(952,000)
Repayment of unsecured senior bank term loan					(25,000)	(125,000)
Transfers to/from parent company					0	0
Change in restricted cash related to financing activities					(4,737)	375
Payment of loan fees					(4,182)	(7,989)
Proceeds from the issuance of common stock					5,052	0
Dividends on common stock					(162,280)	(150,540)
Dividends on preferred stock					(18,740)	(19,414)
Contributions by noncontrolling interests					340	19,410
Distributions to and purchases of noncontrolling interests					(62,973)	(3,487)
Net cash provided by financing activities					301,638	229,980
Effect of foreign exchange rate changes on cash and cash equivalents					(187)	(1,438)
Net (decrease) increase in cash and cash equivalents					(9,628)	9,327
Cash and cash equivalents at beginning of period			$ 86,011		86,011	57,696
Cash and cash equivalents at end of period	86,011	76,383		67,023	76,383	67,023
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest, net of interest capitalized					64,197	33,783
Non-Cash Investing Activities
Change in accrued construction					7,305	(36,235)
Assumption of secured notes payable in connection with purchase of properties					(82,000)	(48,329)
Payable for purchase of noncontrolling interest					(51,887)	0
Alexandria Real Estate Equities, Inc. (Issuer)
Operating Activities
Net income		39,529		34,603	102,212	108,966
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		1,799		1,408	4,515	4,335
Loss on early extinguishment of debt				525	189	525
Impairment of real estate					0
Equity in earnings of unconsolidated joint ventures		0			0
Distributions of earnings from unconsolidated joint ventures					0
Gain on sale of land parcel				0		0
Amortization of loan fees					5,717	5,424
Amortization of debt premiums/discounts					243	152
Amortization of acquired below-market leases					0	0
Deferred rent					0	0
Stock compensation expense					12,922	9,372
Equity in earnings of affiliates		(71,954)		(60,415)	(193,480)	(180,275)
Investment gains					0	0
Investment losses					0	0
Changes in operating assets and liabilities:
Restricted cash					(28)	(15)
Tenant receivables					0	0
Deferred leasing costs					0	(80)
Other assets					(9,228)	(5,263)
Accounts payable, accrued expenses, and tenant security deposits					31,895	50,210
Net cash provided by operating activities					(45,043)	(6,649)
Investing Activities
Proceeds from sale of properties					0	0
Additions to real estate					0	0
Purchase of real estate					0	0
Deposits for investing activities					0	0
Change in restricted cash related to construction projects						0
Investment in unconsolidated real estate joint ventures					0	0
Investments in subsidiaries					(302,455)	(322,228)
Additions to investments					0	0
Sales of investments					0	0
Repayment of notes receivable					0	0
Net cash used in investing activities					(302,455)	(322,228)
Financing Activities
Borrowings from secured notes payable					0	0
Repayments of borrowings from secured notes payable					0	0
Proceeds from issuance of unsecured senior notes payable						698,908
Principal borrowings from unsecured senior line of credit					1,432,000	890,000
Repayments of borrowings from unsecured senior line of credit					(893,000)	(952,000)
Repayment of unsecured senior bank term loan					(25,000)	(125,000)
Transfers to/from parent company					1,853	103
Change in restricted cash related to financing activities					0	0
Payment of loan fees					(2,140)	(6,515)
Proceeds from the issuance of common stock					5,052
Dividends on common stock					(162,280)	(150,540)
Dividends on preferred stock					(18,740)	(19,414)
Contributions by noncontrolling interests					0	0
Distributions to and purchases of noncontrolling interests					0	0
Net cash provided by financing activities					337,745	335,542
Effect of foreign exchange rate changes on cash and cash equivalents					0	0
Net (decrease) increase in cash and cash equivalents					(9,753)	6,665
Cash and cash equivalents at beginning of period			52,491		52,491	14,790
Cash and cash equivalents at end of period	52,491	42,738		21,455	42,738	21,455
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest, net of interest capitalized					47,193	20,089
Non-Cash Investing Activities
Change in accrued construction					0	0
Assumption of secured notes payable in connection with purchase of properties					0	0
Payable for purchase of noncontrolling interest					(51,887)
Alexandria Real Estate Equities, L.P. (Guarantor Subsidiary)
Operating Activities
Net income		63,877		57,117	174,672	170,190
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		0		0	0	0
Loss on early extinguishment of debt			0	0	0	0
Impairment of real estate					0
Equity in earnings of unconsolidated joint ventures		0			0
Distributions of earnings from unconsolidated joint ventures					0
Gain on sale of land parcel				0		0
Amortization of loan fees					0	0
Amortization of debt premiums/discounts					0	0
Amortization of acquired below-market leases					0	0
Deferred rent					0	0
Stock compensation expense					0	0
Equity in earnings of affiliates		(63,964)		(58,381)	(174,800)	(172,989)
Investment gains					0	(3)
Investment losses					269	2,802
Changes in operating assets and liabilities:
Restricted cash					0	0
Tenant receivables					0	0
Deferred leasing costs					0	0
Other assets					0	0
Accounts payable, accrued expenses, and tenant security deposits					0	0
Net cash provided by operating activities					141	0
Investing Activities
Proceeds from sale of properties					0	0
Additions to real estate					0	0
Purchase of real estate					0	0
Deposits for investing activities					0	0
Change in restricted cash related to construction projects						0
Investment in unconsolidated real estate joint ventures					0	0
Investments in subsidiaries					(215,128)	(291,300)
Additions to investments					0	0
Sales of investments					6	0
Repayment of notes receivable					0	0
Net cash used in investing activities					(215,122)	(291,300)
Financing Activities
Borrowings from secured notes payable					0	0
Repayments of borrowings from secured notes payable					0	0
Proceeds from issuance of unsecured senior notes payable						0
Principal borrowings from unsecured senior line of credit					0	0
Repayments of borrowings from unsecured senior line of credit					0	0
Repayment of unsecured senior bank term loan					0	0
Transfers to/from parent company					214,926	291,300
Change in restricted cash related to financing activities					0	0
Payment of loan fees					0	0
Proceeds from the issuance of common stock					0
Dividends on common stock					0	0
Dividends on preferred stock					0	0
Contributions by noncontrolling interests					0	0
Distributions to and purchases of noncontrolling interests					0	0
Net cash provided by financing activities					214,926	291,300
Effect of foreign exchange rate changes on cash and cash equivalents					0	0
Net (decrease) increase in cash and cash equivalents					(55)	0
Cash and cash equivalents at beginning of period			63		63	0
Cash and cash equivalents at end of period	63	8		0	8	0
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest, net of interest capitalized					0	0
Non-Cash Investing Activities
Change in accrued construction					0	0
Assumption of secured notes payable in connection with purchase of properties					0	0
Payable for purchase of noncontrolling interest					0
Combined Non- Guarantor Subsidiaries
Operating Activities
Net income		73,470		64,146	197,979	190,272
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		66,154		56,980	184,529	161,788
Loss on early extinguishment of debt			0	0	0	0
Impairment of real estate					14,510
Equity in earnings of unconsolidated joint ventures		(710)			(1,825)
Distributions of earnings from unconsolidated joint ventures					740
Gain on sale of land parcel				(8)		(805)
Amortization of loan fees					2,631	2,666
Amortization of debt premiums/discounts					(525)	(52)
Amortization of acquired below-market leases					(5,121)	(2,191)
Deferred rent					(34,421)	(35,511)
Stock compensation expense					0	0
Equity in earnings of affiliates		(1,259)		(1,127)	(3,446)	(3,356)
Investment gains					(22,368)	(9,478)
Investment losses					10,888	5,923
Changes in operating assets and liabilities:
Restricted cash					52	15
Tenant receivables					380	(939)
Deferred leasing costs					(47,725)	(25,830)
Other assets					(4,493)	(6,965)
Accounts payable, accrued expenses, and tenant security deposits					(472)	(13,764)
Net cash provided by operating activities					291,313	261,773
Investing Activities
Proceeds from sale of properties					92,455	28,378
Additions to real estate					(362,215)	(345,074)
Purchase of real estate					(248,933)	(97,785)
Deposits for investing activities					(6,707)	(7,292)
Change in restricted cash related to construction projects						6,694
Investment in unconsolidated real estate joint ventures					(7,979)	(67,525)
Investments in subsidiaries					(4,493)	(12,150)
Additions to investments					(67,965)	(35,484)
Sales of investments					39,584	13,883
Repayment of notes receivable					4,264	29,866
Net cash used in investing activities					(561,989)	(486,489)
Financing Activities
Borrowings from secured notes payable					47,375	108,626
Repayments of borrowings from secured notes payable					(12,217)	(228,909)
Proceeds from issuance of unsecured senior notes payable						0
Principal borrowings from unsecured senior line of credit					0	0
Repayments of borrowings from unsecured senior line of credit					0	0
Repayment of unsecured senior bank term loan					0	0
Transfers to/from parent company					305,297	334,275
Change in restricted cash related to financing activities					(4,737)	375
Payment of loan fees					(2,042)	(1,474)
Proceeds from the issuance of common stock					0
Dividends on common stock					0	0
Dividends on preferred stock					0	0
Contributions by noncontrolling interests					340	19,410
Distributions to and purchases of noncontrolling interests					(62,973)	(3,487)
Net cash provided by financing activities					271,043	228,816
Effect of foreign exchange rate changes on cash and cash equivalents					(187)	(1,438)
Net (decrease) increase in cash and cash equivalents					180	2,662
Cash and cash equivalents at beginning of period			33,457		33,457	42,906
Cash and cash equivalents at end of period	33,457	33,637		45,568	33,637	45,568
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest, net of interest capitalized					17,004	13,694
Non-Cash Investing Activities
Change in accrued construction					7,305	(36,235)
Assumption of secured notes payable in connection with purchase of properties					(82,000)	(48,329)
Payable for purchase of noncontrolling interest					0
Eliminations
Operating Activities
Net income		(137,177)		(119,923)	(371,726)	(356,620)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		0		0	0	0
Loss on early extinguishment of debt				0	0	0
Impairment of real estate					0
Equity in earnings of unconsolidated joint ventures		0			0
Distributions of earnings from unconsolidated joint ventures					0
Gain on sale of land parcel				0		0
Amortization of loan fees					0	0
Amortization of debt premiums/discounts					0	0
Amortization of acquired below-market leases					0	0
Deferred rent					0	0
Stock compensation expense					0	0
Equity in earnings of affiliates		137,177		119,923	371,726	356,620
Investment gains					0	0
Investment losses					0	0
Changes in operating assets and liabilities:
Restricted cash					0	0
Tenant receivables					0	0
Deferred leasing costs					0	0
Other assets					0	0
Accounts payable, accrued expenses, and tenant security deposits					0	0
Net cash provided by operating activities					0	0
Investing Activities
Proceeds from sale of properties					0	0
Additions to real estate					0	0
Purchase of real estate					0	0
Deposits for investing activities					0	0
Change in restricted cash related to construction projects						0
Investment in unconsolidated real estate joint ventures					0	0
Investments in subsidiaries					522,076	625,678
Additions to investments					0	0
Sales of investments					0	0
Repayment of notes receivable					0	0
Net cash used in investing activities					522,076	625,678
Financing Activities
Borrowings from secured notes payable					0	0
Repayments of borrowings from secured notes payable					0	0
Proceeds from issuance of unsecured senior notes payable						0
Principal borrowings from unsecured senior line of credit					0	0
Repayments of borrowings from unsecured senior line of credit					0	0
Repayment of unsecured senior bank term loan					0	0
Transfers to/from parent company					(522,076)	(625,678)
Change in restricted cash related to financing activities					0	0
Payment of loan fees					0	0
Proceeds from the issuance of common stock					0
Dividends on common stock					0	0
Dividends on preferred stock					0	0
Contributions by noncontrolling interests					0	0
Distributions to and purchases of noncontrolling interests					0	0
Net cash provided by financing activities					(522,076)	(625,678)
Effect of foreign exchange rate changes on cash and cash equivalents					0	0
Net (decrease) increase in cash and cash equivalents					0	0
Cash and cash equivalents at beginning of period			$ 0		0	0
Cash and cash equivalents at end of period	$ 0	$ 0		$ 0	0	0
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest, net of interest capitalized					0	0
Non-Cash Investing Activities
Change in accrued construction					0	0
Assumption of secured notes payable in connection with purchase of properties					0	$ 0
Payable for purchase of noncontrolling interest					$ 0