Loans Receivable and Allowance for Credit Losses - Troubled Debt Restructurings (Details)	Dec. 31, 2023 USD ($) loan
Additional disclosures
Real estate owned	$ 0
Residential Mortgage \| One- to four-family residential
Additional disclosures
Mortgage loans in process of foreclosure, number of contracts \| loan	2
Mortgage loans in process of foreclosure, total value	$ 227,000

Number of contracts of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process.

No definition available.

+ Details

Name:	tbnk_FinancingReceivableForeclosureNumberOfContractsInProcess
Namespace Prefix:	tbnk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

Name:	tbnk_FinancingReceivableTroubledDebtRestructuringAdditionalDisclosureAbstract
Namespace Prefix:	tbnk_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Recorded investment of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 35
-SubTopic 10
-Topic 310
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-35

+ Details

Name:	us-gaap_MortgageLoansInProcessOfForeclosureAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying amount as of the balance sheet date of land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481990/310-10-45-3

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-11

+ Details

Name:	us-gaap_RealEstateAcquiredThroughForeclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=tbnk_OneToFourFamilyMortgageLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: