Investment Securities: Schedule of Other than Temporary Impairments (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Held to Maturity
Net recoveries on investment securities	$ 9	$ 22	$ 20

Other than Temporary Impairment Losses (Recoveries), Investments, Portion Recognized in Earnings, Net

No definition available.

Name:	tsbk_OtherthanTemporaryImpairmentLossesRecoveriesInvestmentsPortionRecognizedinEarningsNet
Namespace Prefix:	tsbk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration