Debt (Details)							1 Months Ended
	Oct. 31, 2014 USD ($)	Jan. 09, 2014 USD ($) Extension_Option	Sep. 07, 2012	Mar. 29, 2012 USD ($)	Jan. 10, 2012	Mar. 07, 2011	Oct. 31, 2012	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Oct. 10, 2012 USD ($)	Jan. 19, 2011 USD ($)
Debt Instrument [Line Items]
Unsecured notes payable								$ 250,000,000	$ 0
Line of Credit
Debt Instrument [Line Items]
Maximum leverage ratio of revolving credit facility		60.00%
Percent of net proceeds of any additional equity issuances in relation to net proceeds as of Offering		75.00%
Percentage annual distributions cannot exceed funds from operations		95.00%
Maximum unsecured leverage ratio (in percents)		60.00%
Minimum tangible net worth		$ 721,160,000.00
Maximum recourse indebtedness of total asset value (in percents)		15.00%
Base Rate | Line of Credit
Debt Instrument [Line Items]
Points added to federal funds rate (in percents)		0.50%
Points added to Eurodollar rate (in percents)		1.00%
Prior to December 31, 2015 | Line of Credit
Debt Instrument [Line Items]
Maximum secured leverage ratio on revolving credit facility		45.00%
After December 31, 2015 | Line of Credit
Debt Instrument [Line Items]
Minimum fixed charge coverage ratio on revolving credit facility		1.5
Maximum secured leverage ratio on revolving credit facility		40.00%
Minimum unsecured interest coverage ratio (in percents)		175.00%
American Assets Trust, L.P.
Debt Instrument [Line Items]
Non-recourse mortgage loan							10 years
Original principal amount of non-recourse mortgage loan										$ 111,000,000.0
Maturity date of loan							Nov. 01, 2022
Interest rate							3.98%
Number of year non-recourse mortgage loan				7 years
Principal of non-recourse mortgage loan				$ 21,900,000.0
Stated Interest Rate				3.94%
Revolving credit facility borrowing limit, maximum borrowing capacity		$ 350,000,000									$ 250,000,000.0
Years, maximum maturities of securities						30 years
Year, extension on term of revolving credit facility					1 year
Percent of secured indebtedness of the company's secured total asset value			55.00%
Line of credit facility material acquisition			greater than $100 million
Allowable additional borrowing capacity		250,000,000
Unsecured notes payable								250,000,000	$ 0
American Assets Trust, L.P. | Subject to meeting specified requirements and obtaining additional commitments
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity											$ 400,000,000.0
American Assets Trust, L.P. | Revolving Credit Facility
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity		$ 250,000,000
American Assets Trust, L.P. | Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Extension term (in months)		6 months
Number of extensions available | Extension_Option		2
American Assets Trust, L.P. | Term Loan
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity		$ 100,000,000
Unsecured notes payable		$ 100,000,000
American Assets Trust, L.P. | LIBOR | Line of Credit
Debt Instrument [Line Items]
Variable rate basis		LIBOR
American Assets Trust, L.P. | Base Rate | Line of Credit
Debt Instrument [Line Items]
Variable rate basis		base rate
Prime rate		prime rate
Federal funds rate		federal funds
Eurodollar		Eurodollar
American Assets Trust, L.P. | Minimum | LIBOR | Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)		1.35%
American Assets Trust, L.P. | Minimum | LIBOR | Term Loan | Line of Credit
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)		1.30%
American Assets Trust, L.P. | Minimum | Base Rate | Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)		0.35%
American Assets Trust, L.P. | Minimum | Base Rate | Term Loan | Line of Credit
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)		0.30%
American Assets Trust, L.P. | Maximum | LIBOR | Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)		1.95%
American Assets Trust, L.P. | Maximum | LIBOR | Term Loan | Line of Credit
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)		1.90%
American Assets Trust, L.P. | Maximum | Base Rate | Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)		0.95%
American Assets Trust, L.P. | Maximum | Base Rate | Term Loan | Line of Credit
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)		0.90%
American Assets Trust, L.P. | Note Purchase Agreement | Senior Notes
Debt Instrument [Line Items]
Principal of non-recourse mortgage loan	$ 350,000,000
Debt Instrument, Partial Repayment, Minimum Percentage of Principal	5.00%
Debt Instrument, Prepayment, Percentage of Principal Plus a Stated Amount	100.00%
American Assets Trust, L.P. | Note Purchase Agreement | Senior Notes, Series A
Debt Instrument [Line Items]
Principal of non-recourse mortgage loan	$ 150,000,000
Stated Interest Rate	4.04%
Senior Notes								$ 150,000,000
Effective interest rate (percent)	3.88%
American Assets Trust, L.P. | Note Purchase Agreement | Senior Notes, Series B
Debt Instrument [Line Items]
Principal of non-recourse mortgage loan	$ 100,000,000
Stated Interest Rate	4.45%
American Assets Trust, L.P. | Note Purchase Agreement | Senior Notes, Series C
Debt Instrument [Line Items]
Principal of non-recourse mortgage loan	$ 100,000,000
Stated Interest Rate	4.50%