The amount of forbearance inquiries received.

No definition available.

Name:	tbnk_AmountOfForbearanceInquiriesReceived
Namespace Prefix:	tbnk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of forbearance inquiries received on other loans.

+ References

No definition available.

+ Details

Name:	tbnk_AmountOfForbearanceInquiriesReceivedOnOtherLoans
Namespace Prefix:	tbnk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

Number of financing receivables that have been modified by troubled debt restructurings that are considered impaired as of the end of the period.

+ References

No definition available.

+ Details

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

- Definition

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings considered impaired.

+ References

No definition available.

+ Details

Name:	tbnk_FinancingReceivableModificationsRecordedInvestmentConsideredImpaired
Namespace Prefix:	tbnk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

Percentage of the current loan balance to the current tax-assessed value of the property securing mortgage loans.

+ References

No definition available.

+ Details

Name:	tbnk_PercentageOfCurrentLoanBalanceToCurrentTaxAssessedValueOfProperty
Namespace Prefix:	tbnk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of forbearance inquiries received on other loans of total loans receivable.

+ References

No definition available.

+ Details

Name:	tbnk_PercentageOfForbearanceInquiriesReceivedOnOtherLoansOfTotalLoansReceivable
Namespace Prefix:	tbnk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of forbearance inquiries received on total loans receivable.

+ References

No definition available.

+ Details

Name:	tbnk_PercentageOfForbearanceInquiriesReceivedOnTotalLoansReceivable
Namespace Prefix:	tbnk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of mortgage loans of total loan portfolio balance.

+ References

No definition available.

+ Details

Name:	tbnk_PercentageOfMortgageLoansOfTotalLoanPortfolioBalance
Namespace Prefix:	tbnk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_FinancingReceivableModificationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of financing receivable contracts modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953682-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of unfunded portion of contractual agreement to lend funds to borrower for financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118939409&loc=d3e18794-111554

+ Details

Name:	us-gaap_LoansAndLeasesReceivableImpairedCommitmentToLend
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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5162-111524

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=118952595&loc=d3e4437-111522

+ Details

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

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=tbnk_AccrualLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=tbnk_NonAccrualLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=tbnk_FinancingReceivableTroubledDebtRestructuringMember
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:

- Details

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

Loans Receivable and Allowance for Loan Losses - Troubled Debt Restructurings (Details)	6 Months Ended		12 Months Ended
	Jun. 30, 2020 USD ($) loan	Jun. 30, 2019 loan	Dec. 31, 2019 USD ($) loan
Troubled debt restructurings
Number of loans subsequently defaulted \| loan	0		0
Additional disclosures
Loans modified by troubled debt restructurings considered impaired	$ 1,066,000		$ 1,166,000
Forbearance inquiries received	$ 167,100,000
Percentage of forbearance inquiries received on total loans receivable	10.90%
Percentage of current loan balance to the current tax-assessed value of the property securing mortgage loans	55.80%
Forbearance inquiries received on other loans	$ 6,200,000
Percentage of forbearance inquiries received on other loans of total loans receivable	0.40%
Real estate owned	$ 0		$ 0
Mortgage loans in process of foreclosure, number of contracts \| loan	0		0
Accruing interest
Additional disclosures
Number of loans modified by troubled debt restructurings considered impaired \| loan	3		3
Loans modified by troubled debt restructurings considered impaired	$ 571,000		$ 577,000
Non Accrual Loans
Additional disclosures
Number of loans modified by troubled debt restructurings considered impaired \| loan	2		3
Loans modified by troubled debt restructurings considered impaired	$ 495,000		$ 589,000
Loans modified in troubled debt restructuring
Troubled debt restructurings
Number of Loans \| loan	0	0
Number of loans subsequently defaulted \| loan	0		0
Additional disclosures
Commitments to lend additional funds to borrowers	$ 0
One- to four-family residential
Additional disclosures
Loans modified by troubled debt restructurings considered impaired	1,066,000		$ 1,102,000
Forbearance inquiries received	$ 160,900,000
Percentage of forbearance inquiries received on total loans receivable	10.50%
Percentage of current loan balance to the current tax-assessed value of the property securing mortgage loans	48.80%
Percentage of mortgage loans of total loan portfolio balance	97.00%
One- to four-family residential \| Accruing interest
Additional disclosures
Number of loans modified by troubled debt restructurings considered impaired \| loan	3		3
Loans modified by troubled debt restructurings considered impaired	$ 571,000		$ 577,000
One- to four-family residential \| Non Accrual Loans
Additional disclosures
Number of loans modified by troubled debt restructurings considered impaired \| loan	2		2
Loans modified by troubled debt restructurings considered impaired	$ 495,000		$ 525,000
Home Equity Loans and Lines of Credit
Additional disclosures
Loans modified by troubled debt restructurings considered impaired			$ 64,000
Home Equity Loans and Lines of Credit \| Non Accrual Loans
Additional disclosures
Number of loans modified by troubled debt restructurings considered impaired \| loan			1
Loans modified by troubled debt restructurings considered impaired			$ 64,000