Debt instrument, extension option maturity date

No definition available.

Name:	are_Debtinstrumentextensionoptionmaturitydate
Namespace Prefix:	are_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Earn-out provisions for incremental borrowing

+ References

No definition available.

+ Details

Name:	are_Earnoutprovisionsforincrementalborrowing
Namespace Prefix:	are_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Long-term Debt, Percentage Bearing Fixed Interest, Remaining Commitments

+ References

No definition available.

+ Details

Name:	are_LongtermDebtPercentageBearingFixedInterestRemainingCommitments
Namespace Prefix:	are_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Long-term Debt, Percentage Bearing Variable Interest, Remaining Commitments

+ References

No definition available.

+ Details

Name:	are_LongtermDebtPercentageBearingVariableInterestRemainingCommitments
Namespace Prefix:	are_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Long-term debt, remaining commitments

+ References

No definition available.

+ Details

Name:	are_Longtermdebtremainingcommitments
Namespace Prefix:	are_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Total investments in (A) an entity in which the entity has significant influence, but does not have control, (B) subsidiaries that are not required to be consolidated and are accounted for using the equity and or cost method, and (C) an entity in which the reporting entity shares control of the entity with another party or group. Includes long-term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership.

+ References

+ Details

Name:	us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_EquityMethodInvesteeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=are_MenloGatewayMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=are_A14011413ResearchBoulevardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=are_LongwoodMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=are_A704QuinceOrchardRoadMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=are_A1655and1715ThirdStreetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RealEstatePropertiesAxis=are_InitialownershipinterestMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=are_A145MSecureddebtmaturingon3320Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=are_A25MSecureddebtmaturingon7120Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=are_Secureddebtmaturingon9122Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=are_Secureddebtmaturingon31623Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=are_Secureddebtmaturingon62924Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=are_Secureddebtmaturingon5135Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Consolidated and unconsolidated real estate joint ventures Unconsolidated real estate joint ventures (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Apr. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Investments in unconsolidated real estate joint ventures		$ 169,865	$ 110,618
Weighted-Average Interest Rate at End of Period		3.77%
Long-term Debt		$ 5,210,798
Equity Method Investee
Long-term Debt		271,290
Long-term Debt, Remaining Commitments		401,969
Equity Method Investee \| Menlo Gateway
Investments in unconsolidated real estate joint ventures		97,452
Equity Method Investee \| 1401/1413 Research Boulevard
Investments in unconsolidated real estate joint ventures		$ 7,406
Equity interest percentage (in percent)		65.00%
Equity Method Investee \| 360 Longwood Avenue
Investments in unconsolidated real estate joint ventures		$ 25,393
Equity interest percentage (in percent)		27.50%
Equity Method Investee \| 704 Quince Orchard Road
Investments in unconsolidated real estate joint ventures		$ 4,230
Equity interest percentage (in percent)		56.80%
Equity Method Investee \| 1655 and 1725 Third Street
Investments in unconsolidated real estate joint ventures		$ 35,384
Equity interest percentage (in percent)		10.00%
Initial ownership interest \| Equity Method Investee \| Menlo Gateway
Equity interest percentage (in percent)		25.20%
Secured debt maturing on 3/3/20 \| Equity Method Investee \| Menlo Gateway
Maturity Date		Mar. 01, 2019
Debt instrument, extension option maturity date		Mar. 03, 2020
Weighted-Average Interest Rate at End of Period		4.11%
Long-term Debt		$ 124,382
Long-term Debt, Percentage Bearing Variable Interest, Remaining Commitments		$ 23,454
Secured debt maturing on 7/1/20 \| Equity Method Investee \| 1401/1413 Research Boulevard
Maturity Date		May 17, 2020
Debt instrument, extension option maturity date		Jul. 01, 2020
Weighted-Average Interest Rate at End of Period		5.11%
Long-term Debt		$ 9,784
Long-term Debt, Percentage Bearing Variable Interest, Remaining Commitments		$ 14,733
Secured debt maturing on 9/1/24 \| Equity Method Investee \| 360 Longwood Avenue
Maturity Date		Sep. 01, 2022
Debt instrument, extension option maturity date		Sep. 01, 2024
Stated interest rate (as a percent)		3.32%
Weighted-Average Interest Rate at End of Period		3.61%
Long-term Debt		$ 94,091
Long-term Debt, Percentage Bearing Fixed Interest, Remaining Commitments		17,000
Earn-out provisions for incremental borrowing		$ 48,000
Secured debt maturing on 3/16/23 \| Equity Method Investee \| 704 Quince Orchard Road
Maturity Date		Mar. 16, 2023
Weighted-Average Interest Rate at End of Period		4.26%
Long-term Debt		$ 836
Long-term Debt, Percentage Bearing Variable Interest, Remaining Commitments		$ 13,979
Secured debt maturing on 6/29/24 \| Equity Method Investee \| 1655 and 1725 Third Street
Maturity Date		Jun. 29, 2021
Debt instrument, extension option maturity date		Jun. 29, 2024
Weighted-Average Interest Rate at End of Period		4.82%
Long-term Debt		$ 42,197
Long-term Debt, Percentage Bearing Variable Interest, Remaining Commitments		$ 332,803
London Interbank Offered Rate (LIBOR) \| Secured debt maturing on 3/3/20 \| Equity Method Investee \| Menlo Gateway
Applicable margin (as a percent)		2.50%
London Interbank Offered Rate (LIBOR) \| Secured debt maturing on 7/1/20 \| Equity Method Investee \| 1401/1413 Research Boulevard
Applicable margin (as a percent)		2.50%
London Interbank Offered Rate (LIBOR) \| Secured debt maturing on 3/16/23 \| Equity Method Investee \| 704 Quince Orchard Road
Applicable margin (as a percent)		1.95%
London Interbank Offered Rate (LIBOR) \| Secured debt maturing on 6/29/24 \| Equity Method Investee \| 1655 and 1725 Third Street
Applicable margin (as a percent)		3.70%
Subsequent Event \| Secured debt maturing on 5/1/35 \| Equity Method Investee \| Menlo Gateway
Maturity Date	May 01, 2035
Stated interest rate (as a percent)	4.53%
Long-term Debt	$ 0
Long-term Debt, Percentage Bearing Fixed Interest, Remaining Commitments	$ 157,270