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Regulatory Matters: Schedule of Compliance with Regulatory Capital Requirements for Mortgage Companies (Details) $ in Thousands | Sep. 30, 2025 USD ($) | Sep. 30, 2024 USD ($)
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Timberland Bank |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Tier 1 Leverage Capital, Actual Amount | $ 247,162 | $ 229,206
Tier 1 Leverage Capital, Actual Ratio | 0.125 | 0.120
Tier 1 Leverage Capital, Regulatory Minimum To Be Adequately Capitalized, Amount | $ 79,319 | $ 76,319
Tier 1 Leverage Capital, Regulatory Minimum To Be Adequately Capitalized, Ratio | 0.040 | 0.040
Tier 1 Leverage Capital, To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount | $ 99,148 | $ 95,399
Tier 1 Leverage Capital, To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio | 0.050 | 0.050
Tier 1 Risk-based Capital Ratio, Common Equity, Actual Amount | $ 247,162 | $ 229,206
Tier 1 Risk-based Capital Ratio, Common Equity, Actual Ratio | 19.30% | 18.00%
Tier 1 Risk-based Capital Ratio, Regulatory Minimum To Be Adequately Capitalized, Amount | $ 57,623 | $ 57,318
Tier 1 Risk-based Capital Ratio, Regulatory Minimum To Be Adequately Capitalized, Ratio | 4.50% | 4.50%
Tier 1 Risk-based Capital Ratio, Regulatory Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount | $ 83,234 | $ 82,793
Tier 1 Risk-based Capital Ratio, Regulatory Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio | 6.50% | 6.50%
Tier 1 Risk-based Capital, Actual Amount | $ 247,162 | $ 229,206
Tier 1 Risk-based Capital, Actual Ratio | 0.193 | 0.180
Tier 1 Risk-based Capital, Regulatory Minimum To Be Adequately Capitalized, Amount | $ 76,831 | $ 76,424
Tier 1 Risk-based Capital, Regulatory Minimum To Be Adequately Capitalized, Ratio | 0.060 | 0.060
Tier 1 Risk-based Capital, Regulatory Minimum To Be Well Capitalized, Amount | $ 102,442 | $ 101,899
Tier 1 Risk-based Capital, Regulatory Minimum To Be Well Capitalized, Ratio | 0.080 | 0.080
Total Capital, Actual Amount | $ 263,200 | $ 245,152
Total Capital, Actual Ratio | 0.206 | 0.193
Total Capital, Regulatory Minimum To Be Adequately Capitalized, Amount | $ 102,442 | $ 101,899
Total Capital, Regulatory Minimum To Be Adequately Capitalized, Ratio | 0.080 | 0.080
Total Capital, Regulatory Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount | $ 128,052 | $ 127,374
Total Capital, Regulatory Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio | 0.100 | 0.100
Timberland Bancorp |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Tier 1 Leverage Capital, Actual Amount | $ 248,755 | $ 231,092
Tier 1 Leverage Capital, Actual Ratio | 0.126 | 0.121
Tier 1 Risk-based Capital Ratio, Common Equity, Actual Amount | $ 248,755 | $ 231,092
Tier 1 Risk-based Capital Ratio, Common Equity, Actual Ratio | 19.40% | 18.10%
Tier 1 Risk-based Capital, Actual Amount | $ 248,755 | $ 231,092
Tier 1 Risk-based Capital, Actual Ratio | 0.194 | 0.181
Total Capital, Actual Amount | $ 264,800 | $ 247,044
Total Capital, Actual Ratio | 0.207 | 0.194

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