Regulatory Matters: Schedule of Compliance with Regulatory Capital Requirements for Mortgage Companies (Details) $ in Thousands	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)
Timberland Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Leverage Capital, Actual Amount	$ 202,438	$ 188,512
Tier 1 Leverage Capital, Actual Ratio	0.109	0.107
Tier 1 Leverage Capital, Regulatory Minimum To Be Adequately Capitalized, Amount	$ 74,039	$ 70,240
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	$ 92,549	$ 87,801
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	$ 202,438	$ 188,512
Tier 1 Risk-based Capital Ratio, Common Equity, Actual Ratio	18.00%	20.60%
Tier 1 Risk-based Capital Ratio, Regulatory Minimum To Be Adequately Capitalized, Amount	$ 50,551	$ 41,257
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	$ 73,018	$ 59,593
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	$ 202,438	$ 188,512
Tier 1 Risk-based Capital, Actual Ratio	0.180	0.206
Tier 1 Risk-based Capital, Regulatory Minimum To Be Adequately Capitalized, Amount	$ 67,402	$ 55,009
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	$ 89,869	$ 73,345
Tier 1 Risk-based Capital, Regulatory Minimum To Be Well Capitalized, Ratio	0.080	0.080
Total Capital, Actual Amount	$ 216,446	$ 200,002
Total Capital, Actual Ratio	0.193	0.218
Total Capital, Regulatory Minimum To Be Adequately Capitalized, Amount	$ 89,869	$ 73,345
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	$ 112,336	$ 91,682
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	$ 204,659	$ 191,973
Tier 1 Leverage Capital, Actual Ratio	0.110	0.110
Tier 1 Risk-based Capital Ratio, Common Equity, Actual Amount	$ 204,659	$ 191,973
Tier 1 Risk-based Capital Ratio, Common Equity, Actual Ratio	18.20%	20.90%
Tier 1 Risk-based Capital, Actual Amount	$ 204,659	$ 191,973
Tier 1 Risk-based Capital, Actual Ratio	0.182	0.209
Total Capital, Actual Amount	$ 218,667	$ 203,475
Total Capital, Actual Ratio	0.195	0.222

Tier One Risk Adjusted Capital

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
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