Additional term of revolving credit facility based on specified requirements.

No definition available.

Name:	aat_AdditionalTermOfRevolvingCreditFacilityBasedOnSpecifiedRequirements
Namespace Prefix:	aat_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Credit facility covenants.

+ References

No definition available.

+ Details

Name:	aat_CreditFacilityCovenants
Namespace Prefix:	aat_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	aat_DebtAdditionalTextualAbstract
Namespace Prefix:	aat_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	aat_DebtTextualAbstract
Namespace Prefix:	aat_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Initial term of revolving credit facility.

+ References

No definition available.

+ Details

Name:	aat_InitialTermOfRevolvingCreditFacility
Namespace Prefix:	aat_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility maximum borrowing capacity subject to restriction.

+ References

No definition available.

+ Details

Name:	aat_LineOfCreditFacilityMaximumBorrowingCapacitySubjectToRestriction
Namespace Prefix:	aat_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum leverage percentage of revolving credit facility.

+ References

No definition available.

+ Details

Name:	aat_LineOfCreditFacilityMaximumLeveragePercentage
Namespace Prefix:	aat_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum maturities of securities.

+ References

No definition available.

+ Details

Name:	aat_MaximumMaturitiesOfSecurities
Namespace Prefix:	aat_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum principal amount of recourse indebtedness.

+ References

No definition available.

+ Details

Name:	aat_MaximumPrincipalAmountOfRecourseIndebtedness
Namespace Prefix:	aat_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum Secured Leverage Ratio On Revolving Credit Facility

+ References

No definition available.

+ Details

Name:	aat_MaximumSecuredLeverageRatioOnRevolvingCreditFacility
Namespace Prefix:	aat_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Minimum Fixed Charge Coverage Ratio On Revolving Credit Facility

+ References

No definition available.

+ Details

Name:	aat_MinimumFixedChargeCoverageRatioOnRevolvingCreditFacility
Namespace Prefix:	aat_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage limit on annual distributions in relation to funds from operations.

+ References

No definition available.

+ Details

Name:	aat_PercentageLimitOnAnnualDistributionsInRelationToFundsFromOperations
Namespace Prefix:	aat_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of minimum tangible net worth covenant of credit facility.

+ References

No definition available.

+ Details

Name:	aat_PercentageOfMinimumTangibleNetWorthCovenantOfCreditFacility
Namespace Prefix:	aat_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of net proceeds of additional equity Issuances covenant of credit facility.

+ References

No definition available.

+ Details

Name:	aat_PercentageOfNetProceedsOfAdditionalEquityIssuancesCovenantOfCreditFacility
Namespace Prefix:	aat_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Period of amortization schedule.

+ References

No definition available.

+ Details

Name:	aat_PeriodOfAmortizationSchedule
Namespace Prefix:	aat_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Seven year non recourse mortgage loan.

+ References

No definition available.

+ Details

Name:	aat_SevenYearNonRecourseMortgageLoan
Namespace Prefix:	aat_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Years twenty year amortization schedule.

+ References

No definition available.

+ Details

Name:	aat_YearsTwentyYearAmortizationSchedule
Namespace Prefix:	aat_
Data Type:	xbrli:durationItemType
Balance Type:	na
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 FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400

Reference 3: 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.

+ Details

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

- Definition

Interest rate stated in the contractual debt agreement.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: 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

+ Details

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

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ 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 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
Namespace Prefix:	us-gaap_
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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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

Debt (Details Textual) (USD $)	6 Months Ended
Debt (Details Textual) (USD $)	Jun. 30, 2012	Apr. 01, 2019	Mar. 29, 2012	Jan. 10, 2012	Mar. 07, 2011	Jan. 19, 2011
Debt (Textual) [Abstract]
Number of year amortization schedule	30 years
Maximum leverage ratio of revolving credit facility				60.00%
Maximum secured leverage ratio on revolving credit facility				50.00%
Debt (Additional Textual) [Abstract]
Number of year non-recourse mortgage loan			7 years
Principal of non-recourse mortgage loan			$ 21,900,000
Fixed rate interest on non-recourse loan		3.94%
Revolving credit facility borrowing limit, lower						250,000,000
Years, initial term of revolving credit facility	3 years
Year, extension on term of revolving credit facility	1 year
Revolving credit facility borrowing limit, upper	213,800,000					400,000,000
Line of credit facility maximum borrowing capacity subject to restriction						400,000,000
Minimum fixed charge coverage ratio on revolving credit facility				1.50
Percent minimum tangible net worth in relation to tangible net worth as of Offering						75.00%
Percent of net proceeds of any additional equity issuances in relation to net proceeds as of Offering						85.00%
Maximum principal amount of recourse indebtedness outstanding at any time, aside from revolving credit facility				$ 35,000,000
Percentage annual distributions cannot exceed funds from operations	95.00%
Years, maximum maturities of securities					30 years
Compliance with all loan covenants	Jun. 30, 2012
160 King Street [Member]
Debt (Textual) [Abstract]
Number of year amortization schedule	20 years
Debt (Additional Textual) [Abstract]
Fixed rate interest on non-recourse loan	5.68%
Alamo Quarry Market [Member]
Debt (Additional Textual) [Abstract]
Fixed rate interest on non-recourse loan	5.67%
Torrey Reserve - North Court [Member]
Debt (Additional Textual) [Abstract]
Fixed rate interest on non-recourse loan	7.22%
Torrey Reserve-VCI, VCII, VCIII [Member]
Debt (Additional Textual) [Abstract]
Fixed rate interest on non-recourse loan	6.36%
Solana Beach Corporate Centre III-IV[Member]
Debt (Additional Textual) [Abstract]
Fixed rate interest on non-recourse loan	6.39%
Solana Beach Towne Centre [Member]
Debt (Additional Textual) [Abstract]
Fixed rate interest on non-recourse loan	5.91%