Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Description of award terms as to how many shares or portion of an award are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, thereby giving the employee the legal right to convert the award to shares, to sell the shares, and be entitled to the cash proceeds of such sale. For example, vesting may be expressed as being 25 percent of the shares under option on each anniversary of the grant date.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- 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.

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No definition available.

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Percentage of vesting of share-based compensation awards.

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Equity of American Assets Trust, Inc. Restricted Common Stock Issued (Details) - Restricted Stock - $ / shares									3 Months Ended
	Dec. 01, 2015	Jun. 16, 2015	Dec. 01, 2014	Jun. 17, 2014	Mar. 25, 2014	Jul. 13, 2013	Jul. 10, 2012	Jan. 19, 2012	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights								2
Award vesting period									3 years
Award vesting percentage	33.30%		33.30%		33.30%	33.30%	33.30%
Granted, Weighted Average Grant Date Fair Value (in USD per share)		$ 39.64		$ 34.10		$ 31.97	$ 25.05
Granted, Shares	93,310	5,044	98,765	5,864	112,119	5,004	8,015	2,000
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Weighted Average Grant Date Fair Value (in USD per share)	$ 13,670.00		$ 36.28		$ 28.89			$ 11.91
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Weighted Average Grant Date Fair Value (in USD per share)	$ 26,390.00		$ 36.32		$ 31.25			$ 12.61