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DEBT - Summary of Total Unsecured Notes Payable Outstanding (Details) $ in Thousands | Sep. 10, 2024 USD ($) | Jul. 17, 2019 USD ($) | May 11, 2017 USD ($) | Jan. 18, 2017 USD ($) | Sep. 30, 2025 USD ($) interest_rate_swap_agreement | Dec. 31, 2024 USD ($) | Sep. 17, 2024 | Sep. 09, 2024 USD ($) | Jan. 26, 2021 | Jul. 30, 2019 | May 23, 2017 | Mar. 01, 2017
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Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Debt discount and issuance costs, net of accumulated amortization of $8,186 and $9,890, respectively |  |  |  |  | $ (162) | $ (648) |  |  |  |  |  |
Accumulated amortization |  |  |  |  | 2,429 | 1,943 |  |  |  |  |  |
American Assets Trust, L.P. | Treasury Lock |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Gain on derivatives |  | $ 500 | $ 700 | $ 10,400 |  |  |  |  |  |  |  |
Notional amount | $ 150,000 |  |  |  |  |  |  | $ 150,000 |  |  |  |
Loss on derivatives | $ 1,300 |  |  |  |  |  |  |  |  |  |  |
American Assets Trust, L.P. | Unsecured term loans, net |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Principal Balance |  |  |  |  | 1,625,000 | 1,950,000 |  |  |  |  |  |
Debt discount and issuance costs, net of accumulated amortization of $8,186 and $9,890, respectively |  |  |  |  | (12,772) | (14,244) |  |  |  |  |  |
Total Secured Notes Payable Outstanding |  |  |  |  | 1,612,228 | 1,935,756 |  |  |  |  |  |
Accumulated amortization |  |  |  |  | $ 8,186 | 9,890 |  |  |  |  |  |
American Assets Trust, L.P. | Term Loan A | Interest Rate Swap |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of interest rate agreements | interest_rate_swap_agreement |  |  |  |  | 2 |  |  |  |  |  |  |
Fixed interest rate on derivative |  |  |  |  | 2.70% |  |  |  |  |  |  |
American Assets Trust, L.P. | Term Loan A | Unsecured term loans, net |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Principal Balance |  |  |  |  | $ 100,000 | 100,000 |  |  |  |  |  |
American Assets Trust, L.P. | Term Loan B | Unsecured term loans, net |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Principal Balance |  |  |  |  | 0 | 150,000 |  |  |  |  |  |
American Assets Trust, L.P. | Term Loan C | Unsecured term loans, net |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Principal Balance |  |  |  |  | 0 | 75,000 |  |  |  |  |  |
American Assets Trust, L.P. | Senior Guaranteed Notes, Series C | Unsecured term loans, net |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Principal Balance |  |  |  |  | $ 0 | 100,000 |  |  |  |  |  |
Stated Interest Rate |  |  |  |  | 4.50% |  |  |  |  |  |  |
American Assets Trust, L.P. | Senior Guaranteed Notes, Series D | Treasury Lock |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Effective interest rate |  |  |  |  | 3.87% |  |  |  |  |  |  |
American Assets Trust, L.P. | Senior Guaranteed Notes, Series D | Unsecured term loans, net |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Principal Balance |  |  |  |  | $ 250,000 | 250,000 |  |  |  |  |  |
Stated Interest Rate |  |  |  |  | 4.29% |  |  |  |  |  |  | 4.29%
American Assets Trust, L.P. | Senior Guaranteed Notes, Series E | Treasury Lock |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Effective interest rate |  |  |  |  | 4.18% |  |  |  |  |  |  |
American Assets Trust, L.P. | Senior Guaranteed Notes, Series E | Unsecured term loans, net |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Principal Balance |  |  |  |  | $ 100,000 | 100,000 |  |  |  |  |  |
Stated Interest Rate |  |  |  |  | 4.24% |  |  |  |  |  | 4.24% |
American Assets Trust, L.P. | Senior Guaranteed Notes, Series G | Treasury Lock |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Effective interest rate |  |  |  |  | 3.88% |  |  |  |  |  |  |
American Assets Trust, L.P. | Senior Guaranteed Notes, Series G | Unsecured term loans, net |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Principal Balance |  |  |  |  | $ 150,000 | 150,000 |  |  |  |  |  |
Stated Interest Rate |  |  |  |  | 3.91% |  |  |  |  | 3.91% |  |
American Assets Trust, L.P. | 3.375% Senior Notes |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Stated Interest Rate |  |  |  |  |  |  |  |  | 3.375% |  |  |
American Assets Trust, L.P. | 3.375% Senior Notes | Unsecured term loans, net |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Principal Balance |  |  |  |  | $ 500,000 | 500,000 |  |  |  |  |  |
Stated Interest Rate |  |  |  |  | 3.375% |  |  |  | 3.375% |  |  |
Effective interest rate |  |  |  |  |  |  |  |  | 3.502% |  |  |
American Assets Trust, L.P. | 6.150% Senior Notes |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Stated Interest Rate |  |  |  |  |  |  | 6.15% |  |  |  |  |
American Assets Trust, L.P. | 6.150% Senior Notes | Treasury Lock |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Effective interest rate |  |  |  |  | 6.209% |  |  |  |  |  |  |
American Assets Trust, L.P. | 6.150% Senior Notes | Unsecured term loans, net |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Principal Balance |  |  |  |  | $ 525,000 | $ 525,000 |  |  |  |  |  |
Stated Interest Rate |  |  |  |  | 6.15% |  | 6.15% |  |  |  |  |
Effective interest rate |  |  |  |  |  |  | 6.194% |  |  |  |  |
American Assets Trust, L.P. | Term Loan B & Term Loan C | Interest Rate Swap | First period |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Fixed interest rate on derivative |  |  |  |  | 5.47% |  |  |  |  |  |  |
American Assets Trust, L.P. | Term Loan B & Term Loan C | Interest Rate Swap | Second period |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Fixed interest rate on derivative |  |  |  |  | 5.57% |  |  |  |  |  |  |

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