Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income (loss)	$ 194,204	$ (49,799)	$ 146,114
Unrealized (losses) gains on marketable securities:
Unrealized holding gains (losses) arising during the period	(24,360)	79,833	(77,370)
Reclassification adjustment for losses (gains) included in net income	6,118	(18,473)	(12,138)
Unrealized gains (losses) on available-for-sale equity securities, net	30,478	(98,306)	65,232
Unrealized gains (losses) on interest rate swaps:
Unrealized interest rate swap gains (losses) arising during the year	2,837	(1,150)	(5,516)
Reclassification adjustment for amortization of interest expense included in net income	1,915	5,273	2,707
Unrealized gains (losses) on interest rate swap agreements, net	4,752	4,123	(2,809)
Unrealized gains (losses) on foreign currency translations:
Unrealized foreign currency translation gains (losses) during the year	7,774	(2,579)	(21,844)
Reclassification adjustment for gains included in net income	1,599	52,926	9,236
Unrealized gains (losses) on foreign currency translation, net	9,373	50,347	(12,608)
Total other comprehensive income (loss)	44,603	(43,836)	49,815
Comprehensive income (loss)	238,807	(93,635)	195,929
Less: comprehensive income attributable to noncontrolling interests	(25,045)	(16,102)	(1,893)
Comprehensive income attributable to Alexandria’s common stockholders	213,762	(109,737)	194,036
Alexandria Real Estate Equities, Inc. (Issuer)
Net income (loss)	169,093	(65,901)	144,217
Unrealized (losses) gains on marketable securities:
Unrealized holding gains (losses) arising during the period	0	0	0
Reclassification adjustment for losses (gains) included in net income	0	0	0
Unrealized gains (losses) on available-for-sale equity securities, net	0	0	0
Unrealized gains (losses) on interest rate swaps:
Unrealized interest rate swap gains (losses) arising during the year	3,025	(1,338)	(5,516)
Reclassification adjustment for amortization of interest expense included in net income	1,914	5,272	2,707
Unrealized gains (losses) on interest rate swap agreements, net	4,939	3,934	(2,809)
Unrealized gains (losses) on foreign currency translations:
Unrealized foreign currency translation gains (losses) during the year	0	0	0
Reclassification adjustment for gains included in net income	0	0	0
Unrealized gains (losses) on foreign currency translation, net	0	0	0
Total other comprehensive income (loss)	4,939	3,934	(2,809)
Comprehensive income (loss)	174,032	(61,967)	141,408
Less: comprehensive income attributable to noncontrolling interests	0	0	0
Comprehensive income attributable to Alexandria’s common stockholders	174,032	(61,967)	141,408
Alexandria Real Estate Equities, L.P. (Guarantor Subsidiary)
Net income (loss)	325,655	47,362	238,486
Unrealized (losses) gains on marketable securities:
Unrealized holding gains (losses) arising during the period	5	(135)	21
Reclassification adjustment for losses (gains) included in net income	2	(148)	1
Unrealized gains (losses) on available-for-sale equity securities, net	(3)	(13)	(20)
Unrealized gains (losses) on interest rate swaps:
Unrealized interest rate swap gains (losses) arising during the year	0	0	0
Reclassification adjustment for amortization of interest expense included in net income	0	0	0
Unrealized gains (losses) on interest rate swap agreements, net	0	0	0
Unrealized gains (losses) on foreign currency translations:
Unrealized foreign currency translation gains (losses) during the year	0	0	0
Reclassification adjustment for gains included in net income	0	0	0
Unrealized gains (losses) on foreign currency translation, net	0	0	0
Total other comprehensive income (loss)	(3)	(13)	(20)
Comprehensive income (loss)	325,652	47,349	238,466
Less: comprehensive income attributable to noncontrolling interests	0	0	0
Comprehensive income attributable to Alexandria’s common stockholders	325,652	47,349	238,466
Combined Non- Guarantor Subsidiaries
Net income (loss)	371,993	98,275	274,962
Unrealized (losses) gains on marketable securities:
Unrealized holding gains (losses) arising during the period	(24,365)	79,968	(77,391)
Reclassification adjustment for losses (gains) included in net income	6,116	(18,325)	(12,139)
Unrealized gains (losses) on available-for-sale equity securities, net	30,481	(98,293)	65,252
Unrealized gains (losses) on interest rate swaps:
Unrealized interest rate swap gains (losses) arising during the year	(188)	188	0
Reclassification adjustment for amortization of interest expense included in net income	1	1	0
Unrealized gains (losses) on interest rate swap agreements, net	(187)	189	0
Unrealized gains (losses) on foreign currency translations:
Unrealized foreign currency translation gains (losses) during the year	7,774	(2,579)	(21,844)
Reclassification adjustment for gains included in net income	1,599	52,926	9,236
Unrealized gains (losses) on foreign currency translation, net	9,373	50,347	(12,608)
Total other comprehensive income (loss)	39,667	(47,757)	52,644
Comprehensive income (loss)	411,660	50,518	327,606
Less: comprehensive income attributable to noncontrolling interests	(25,045)	(16,102)	(1,893)
Comprehensive income attributable to Alexandria’s common stockholders	386,615	34,416	325,713
Consolidation, Eliminations
Net income (loss)	(672,537)	(129,535)	(511,551)
Unrealized (losses) gains on marketable securities:
Unrealized holding gains (losses) arising during the period	0	0	0
Reclassification adjustment for losses (gains) included in net income	0	0	0
Unrealized gains (losses) on available-for-sale equity securities, net	0	0	0
Unrealized gains (losses) on interest rate swaps:
Unrealized interest rate swap gains (losses) arising during the year	0	0	0
Reclassification adjustment for amortization of interest expense included in net income	0	0	0
Unrealized gains (losses) on interest rate swap agreements, net	0	0	0
Unrealized gains (losses) on foreign currency translations:
Unrealized foreign currency translation gains (losses) during the year	0	0	0
Reclassification adjustment for gains included in net income	0	0	0
Unrealized gains (losses) on foreign currency translation, net	0	0	0
Total other comprehensive income (loss)	0	0	0
Comprehensive income (loss)	(672,537)	(129,535)	(511,551)
Less: comprehensive income attributable to noncontrolling interests	0	0	0
Comprehensive income attributable to Alexandria’s common stockholders	$ (672,537)	$ (129,535)	$ (511,551)