The number of real estate properties held for sale as of the balance sheet date.

No definition available.

Name:	are_NumberOfRealEstatePropertiesHeldForSale
Namespace Prefix:	are_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the percentage of assets held for sale occupied by a user.

+ References

No definition available.

+ Details

Name:	are_PercentageOfPropertyOccupied
Namespace Prefix:	are_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the estimated sale price per rentable square foot of real estate property

+ References

No definition available.

+ Details

Name:	are_PricePerSquareFoot
Namespace Prefix:	are_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the estimated sale price per developable square foot of real estate held for sale.

+ References

No definition available.

+ Details

Name:	are_RealEstateHeldforsaleEstimatedSalePricePerSquareFoot
Namespace Prefix:	are_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	are_SignificantDisposalsLineItems
Namespace Prefix:	are_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the square footage area related to a rental real estate property.

+ References

No definition available.

+ Details

Name:	are_SquareFootageOfPropertiesAvailableForDevelopmentAndRent
Namespace Prefix:	are_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of rentable square feet related to rental properties held for sale, net.

+ References

No definition available.

+ Details

Name:	are_SquareFootageOfRentalPropertiesHeldForSaleNet
Namespace Prefix:	are_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

This element represents the amount of gain (loss) on sale of properties during the reporting period net of the applicable income taxes realized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 15

-Paragraph a

-Subparagraph 1(ii)

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 974

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-15.(a)(1)(ii))

-URI http://asc.fasb.org/extlink&oid=6875705&loc=d3e641549-123027

+ Details

Name:	us-gaap_GainLossOnSaleOfPropertiesNetOfApplicableIncomeTaxes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The charge against earnings in the period to reduce the carrying amount of real property to fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6391110&loc=d3e2921-110230

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 144

-Paragraph 26

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_ImpairmentOfRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount representing an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date. Such amount may include accrued interest receivable in accordance with the terms of the note. The note also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. Excludes amounts related to receivables held-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.10(3))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 10

-Subparagraph 3

-Article 9

+ Details

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

- Definition

Cash received for the sale of real estate that is not part of an investing activity during the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3179-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 24

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_ProceedsFromSaleOfRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Investments in real estate (Details 3) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended
Investments in real estate (Details 3) (USD $)	Jul. 30, 2012	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Dispositions
Total Sales Price	$ 19,800,000			$ 75,080,000
Gain on sale of land parcel			46,000	1,864,000	46,000
Total impairment charges		9,799,000	994,000	9,799,000	994,000
Secured note receivable		6,100,000		6,100,000
Significant observable input (level 2)
Dispositions
Impairment of real estate assets held for sale		4		4
Rentable square feet related to rental properties held for sale		504,130		504,130
Total impairment charges		9,800,000
Sale of land parcels and assets with a previous operating component
Dispositions
Total Sales Price				45,530,000
1201/1209 Mercer Street
Dispositions
Rentable/ Developable Square Feet		76,029		76,029
Sales Price per SF				73
Total Sales Price				5,570,000
Gain on sale of land parcel				54,000
801 Dexter Avenue North
Dispositions
Rentable/ Developable Square Feet		120,000		120,000
Sales Price per SF				72
Total Sales Price				8,600,000
Gain on sale of land parcel				55,000
Land parcel
Dispositions
Rentable/ Developable Square Feet		(3)		(3)
Sales Price per SF				275
Total Sales Price				31,360,000
Gain on sale of land parcel				1,864,000
Estimated sale price per developable square foot				275
Sales of income-producing properties
Dispositions
Total Sales Price				29,550,000
200 Lawrence Drive/210 Welsh Pool Road
Dispositions
Rentable/ Developable Square Feet		210,866		210,866
Sales Price per SF				94
Total Sales Price				19,750,000
Gain on sale of land parcel				103,000
Rentable square feet related to rental properties held for sale		38,513		38,513
Property occupied (as a percent)				18.00%
Secured note receivable		6,100,000		6,100,000
155 Fortune Blvd.
Dispositions
Rentable/ Developable Square Feet		36,000		36,000
Sales Price per SF				222
Total Sales Price				8,000,000
Gain on sale of land parcel				1,350,000
5110 Campus Drive
Dispositions
Rentable/ Developable Square Feet		21,000		21,000
Sales Price per SF				86
Total Sales Price		1,800,000		1,800,000
Gain on sale of land parcel				$ 2,000