The amended principal amount of the debt instrument.

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Period Type:	instant

- Definition

Length of the extension period for the maturity date on the debt instrument, assuming we exercise our sole right to extend the maturity date.

+ Details

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Period Type:	duration

- Definition

Reflects the calculation as of the balance sheet date of the average interest rate weighted by the amount of debt outstanding at that time, including the impact of interest rate swap agreements.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount available under our accordion option to increase the maximum borrowing capacity under the credit facility.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Aggregate of amount borrowed under the unsecured line of credit and unsecured term loan as of the balance sheet date.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The number of times which the maturity date of the unsecured line of credit can be extended.

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the maximum leverage ratio allowable under the financial covenants related to our unsecured line of credit and unsecured term loans.

+ Details

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Period Type:	instant

- Definition

Represents the maximum secured debt ratio allowable under the financial covenants related to our unsecured line of credit and unsecured term loans.

+ Details

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Period Type:	instant

- Definition

Represents the maximum unsecured leverage ratio allowable under the financial covenants related to our unsecured line of credit and unsecured term loans.

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Represents the minimum book value allowable under the financial covenants related to our unsecured line of credit and unsecured term loans.

+ Details

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Balance Type:	debit
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- Definition

Represents the minimum fixed charge coverage ratio allowable under the financial covenants related to our unsecured line of credit and unsecured term loans.

+ Details

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Period Type:	instant

- Definition

Represents the percentage of the net proceeds of equity offering added to minimum book value for financial covenants related to our unsecured line of credit and unsecured term loans.

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Represents the minimum unsecured debt yield allowable under the financial covenants related to our unsecured line of credit and term loans.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the minimum unsecured debt yield allowable under the financial covenants related to our unsecured line of credit and unsecured term loans.

+ Details

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Namespace Prefix:	are
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ Details

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Period Type:	duration

- Definition

The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 21
-Paragraph 16, 20
-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.

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=6451184&loc=d3e28551-108399

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-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Increase for additional borrowings on the debt instrument during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 4
-Section 08
-Paragraph f

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

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Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount represents the difference between the fair value of the payments made and the carrying amount of the debt at the time of its extinguishment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6850294&loc=d3e12355-112629

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Principles Board Opinion (APB)
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-Paragraph 20, 21
-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.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
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-Topic 470
-SubTopic 50
-Section 40
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6850294&loc=d3e12317-112629

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Period Type:	duration

- Definition

Amount borrowed under the credit facility as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 22
-Article 5

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 129
-Paragraph 2, 4
-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.

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-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
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- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 5
-Section 02
-Subsection 19, 20, 22

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 16
-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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Unsecured line of credit and unsecured term loans (Details) (USD $)	3 Months Ended		6 Months Ended			1 Months Ended			1 Months Ended				1 Months Ended	6 Months Ended		1 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010	Jan. 31, 2011 Unsecured Credit Facility	Jun. 30, 2011 Unsecured Credit Facility	May 02, 2007 Unsecured Credit Facility	Jan. 31, 2011 Unsecured Credit Facility Line of Credit	Jun. 30, 2011 Unsecured Credit Facility Line of Credit	Dec. 31, 2010 Unsecured Credit Facility Line of Credit	May 02, 2007 Unsecured Credit Facility Line of Credit	Jan. 31, 2011 2012 Unsecured Term Loan	Jun. 30, 2011 2012 Unsecured Term Loan	Dec. 31, 2010 2012 Unsecured Term Loan	Jun. 30, 2011 2016 Unsecured Term Loan	Feb. 28, 2011 2016 Unsecured Term Loan	Jun. 30, 2011 2016 Unsecured Term Loan
Unsecured line of credit and unsecured term loans
Unsecured credit facility maximum permitted borrowings						$ 2,250,000,000		$ 1,900,000,000	$ 1,500,000,000			$ 1,150,000,000	$ 750,000,000
Borrowings outstanding										575,000,000	748,000,000
Borrowings														250,000,000	750,000,000	750,000,000		750,000,000
Outstanding unsecured line of credit and unsecured term loans	1,575,000,000		1,575,000,000		1,498,000,000
Borrowings																	250,000,000
Unsecured term loan, face amount																250,000,000		250,000,000
Accordion option to increase commitments under the Unsecured Credit Facility						300,000,000
Base rate						LIBOR or the specified base rate												LIBOR or the specified base rate
Applicable margin (as a percent)										2.40%				1.00%		1.75%		1.75%
Weighted average interest rate, including the impact of interest rate swap agreements (as a percent)							3.60%
Number of extensions to maturity date									2
Length of maturity date extension period									6M				1Y			1Y
Leverage Ratio, maximum (as a percent)						60.00%
Unsecured Leverage Ratio, maximum (as a percent)						60.00%
Fixed Charge Coverage, minimum						1.5
Unsecured Debt Yield, minimum (as a percent)						11.00%
Unsecured Debt Yield after June 30, 2011, minimum (as a percent)						12.00%
Minimum Book Value						2,000,000,000
Minimum percentage of the net proceeds of equity (as a percent)						50.00%
Secured Debt Ratio, maximum (as a percent)						40.00%
Debt Instrument Amended Face Amount																750,000,000		750,000,000
Loss on early extinguishment of debt	$ (1,248,000)	$ (41,496,000)	$ (3,743,000)	$ (41,496,000)										$ 1,200,000