Property expenses.

No definition available.

Name:	aat_PropertyExpenses
Namespace Prefix:	aat_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

+ References

+ Details

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

- Definition

The net result for the period of deducting operating expenses from operating revenues.

+ References

No definition available.

+ Details

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

- Definition

The aggregate revenue from real estate operations during the reporting period.

+ 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=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_RealEstateRevenueNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_SegmentReportingInformationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Details

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

- Details

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

- Details

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

Segment Reporting Operating Activity Within Reportable Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Operating income (loss)	$ 22,526us-gaap_OperatingIncomeLoss	$ 23,036us-gaap_OperatingIncomeLoss	$ 17,726us-gaap_OperatingIncomeLoss	$ 20,381us-gaap_OperatingIncomeLoss	$ 20,407us-gaap_OperatingIncomeLoss	$ 21,441us-gaap_OperatingIncomeLoss	$ 19,373us-gaap_OperatingIncomeLoss	$ 19,880us-gaap_OperatingIncomeLoss	$ 83,669us-gaap_OperatingIncomeLoss	$ 81,101us-gaap_OperatingIncomeLoss	$ 71,906us-gaap_OperatingIncomeLoss
Gross Profit									168,769us-gaap_GrossProfit	165,071us-gaap_GrossProfit	149,352us-gaap_GrossProfit
Total Retail
Segment Reporting Information [Line Items]
Property revenue									96,140	93,449	91,991
Property expense									(25,451)	(23,900)	(24,955)
Operating income (loss)									70,689	69,549	67,036
Total Office
Segment Reporting Information [Line Items]
Property revenue									92,474	90,527	78,101
Property expense									(27,003)	(26,688)	(23,780)
Operating income (loss)									65,471	63,839	54,321
Total Multifamily
Segment Reporting Information [Line Items]
Property revenue									16,976	16,125	14,852
Property expense									(6,099)	(5,917)	(5,914)
Operating income (loss)									10,877	10,208	8,938
Total Mixed-Use
Segment Reporting Information [Line Items]
Property revenue									54,410	54,956	50,522
Property expense									(32,678)	(33,481)	(31,465)
Operating income (loss)									$ 21,732	$ 21,475	$ 19,057