Component of Rental Income and Expense Components of Rental Income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Rental Income [Line Items]
Cost reimbursement	$ 29,052us-gaap_TenantReimbursements	$ 27,583us-gaap_TenantReimbursements	$ 27,763us-gaap_TenantReimbursements
Percentage rent	3,107us-gaap_PercentageRent	2,655us-gaap_PercentageRent	2,608us-gaap_PercentageRent
Hotel revenue	33,911us-gaap_RevenueFromLeasedAndOwnedHotels	35,137us-gaap_RevenueFromLeasedAndOwnedHotels	31,729us-gaap_RevenueFromLeasedAndOwnedHotels
Other	1,681aat_OtherRealEstateRentalRevenue	1,688aat_OtherRealEstateRentalRevenue	1,597aat_OtherRealEstateRentalRevenue
Total rental income	246,078	242,757	225,249
Total Retail
Rental Income [Line Items]
Minimum rents	70,573	69,374	67,046
Total Office
Rental Income [Line Items]
Minimum rents	82,018	81,845	71,817
Total Multifamily
Rental Income [Line Items]
Minimum rents	15,732	14,926	13,796
Total Mixed-Use
Rental Income [Line Items]
Minimum rents	$ 10,004	$ 9,549	$ 8,893

Other real estate rental revenue.

No definition available.

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

- 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

+ 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=26872669&loc=d3e20235-122688

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

+ 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:	aat_MinimumRentsAxis=aat_MixedUseMember
Namespace Prefix:
Data Type:	na
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Period Type:

- Details

Name:	aat_MinimumRentsAxis=aat_MultiFamilyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	aat_MinimumRentsAxis=aat_OfficeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	aat_MinimumRentsAxis=aat_RetailMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: