Amount recovered for reimbursements of operating expense for related party.

No definition available.

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

- Definition

Percentage of investment in related party.

+ References

No definition available.

+ Details

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Namespace Prefix:	aat_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Term of lessor's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=124258985&loc=SL77919359-209981

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of operating lease income from lease payments and variable lease payments paid and payable to lessor. Includes, but is not limited to, variable lease payments not included in measurement of lease receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=124258985&loc=SL77919372-209981

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=123420820&loc=SL77919311-209978

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section 50
-Paragraph 6A
-URI http://asc.fasb.org/extlink&oid=124502072&loc=SL77927221-108306

+ Details

Name:	us-gaap_OperatingLeaseLeaseIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=aat_WBWCHPLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=aat_AmericanAssetsInc.Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=srt_BoardOfDirectorsChairmanMember
Namespace Prefix:
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Balance Type:
Period Type:

RELATED PARTY TRANSACTIONS (Details) - USD ($) $ in Thousands			3 Months Ended
	Mar. 01, 2021	Mar. 01, 2019	Mar. 31, 2022	Mar. 31, 2021
Related Party Transaction [Line Items]
Rental income			$ 96,986	$ 81,130
Investment in WBW CHP LLC (as a percent)			47.70%
WBW CHP LLC
Related Party Transaction [Line Items]
Amount recovered for reimbursements of operating expense for related party			$ 300	300
American Assets, Inc. \| Board of Directors Chairman
Related Party Transaction [Line Items]
Term of contract (in years)	10 years	3 years
Rental income	$ 200	$ 200	$ 100	$ 100