COMPONENTS OF RENTAL INCOME AND EXPENSE - Component of Rental Income (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Rental Income [Line Items]
Cost reimbursement	$ 8,344	$ 8,049	$ 23,832	$ 22,654
Percentage rent	685	552	1,572	1,277
Hotel revenue	11,371	10,796	30,045	28,531
Other	369	354	1,126	1,137
Total rental income	71,852	67,471	207,318	193,776
Total Retail
Rental Income [Line Items]
Minimum rents	18,524	18,274	55,548	54,741
Total Office
Rental Income [Line Items]
Minimum rents	22,458	22,193	67,427	64,913
Total Multifamily
Rental Income [Line Items]
Minimum rents	7,451	4,650	19,806	12,820
Total Mixed-Use
Rental Income [Line Items]
Minimum rents	$ 2,650	$ 2,603	$ 7,962	$ 7,703

Other real estate rental revenue.

No definition available.

Name:	aat_OtherRealEstateRentalRevenue
Namespace Prefix:	aat_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Rental Income [Line Items]

+ References

No definition available.

+ Details

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

- Definition

The total amount of revenue recognized for the period from operating leases, including minimum lease revenue, contingent revenue, percentage revenue and sublease revenue.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=7501430&loc=d3e39896-112707

+ Details

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

- Definition

The total amount of lease revenue recognized for the period for which the lessee was obligated under leasing arrangements regardless of any other events or conditions. This amount excludes contingent revenue and sublease revenue.

+ References

+ Details

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

- Definition

This element represents the rental revenue earned during the period from lessee-operators based on revenues generated in their operations, generally in excess of a base amount. Such rental revenue is generally stipulated in the lease agreement, usually will provide for a fixed percentage of revenue to be paid as additional (or possibly only) rent due the lessor, and may be based on gross revenues, net revenues, or multiple variations thereof. Percentage rent is often required under leases with retail outlets located on premises owned by hoteliers, cruise lines, others in the hospitality industry, and shopping mall operators, among others.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(e))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

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

- Definition

Amount, net of promotional allowances, of revenue from managing and operating hotels, including, but not limited to, revenue from occupancy, casino, food and beverage, and retail. Excludes operating lease income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(d))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

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

- Definition

In accordance with the provisions of their lease agreement, this element represents allowable charges due a landlord from its tenant. In retail store and office building leases, for example, tenant reimbursements may cover items such as taxes, utilities, and common area expenses.

+ References

+ Details

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

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=aat_RetailSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=aat_OfficeSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=aat_MultifamilySegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=aat_MixedUseSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: