Loans And Allowance For Credit Losses (Schedule Of Financial Effect Of Loan Modifications) (Details) - Real Estate Loans	3 Months Ended
Dec. 31, 2025	Dec. 31, 2024
Minimum \| Residential Non Home Today \| Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, Modified, Weighted Average Interest Rate Decrease from Modification	5.29%	5.73%
Minimum \| Residential Home Today \| Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, Modified, Weighted Average Interest Rate Decrease from Modification	0.00%	4.00%
Minimum \| Home Equity Line of Credit \| Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, Modified, Weighted Average Interest Rate Decrease from Modification	7.25%	6.99%
Minimum \| Home Equity Loan \| Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, Modified, Weighted Average Interest Rate Decrease from Modification	0.00%	0.00%
Maximum \| Residential Non Home Today \| Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, Modified, Weighted Average Interest Rate Decrease from Modification	3.50%	3.50%
Maximum \| Residential Non Home Today \| Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, Modified, Weighted Average Term Increase from Modification	9 years 7 months 6 days	13 years 9 months 18 days
Maximum \| Residential Home Today \| Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, Modified, Weighted Average Interest Rate Decrease from Modification	0.00%	3.50%
Maximum \| Residential Home Today \| Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, Modified, Weighted Average Term Increase from Modification	11 years 7 months 6 days	9 years 9 months 18 days
Maximum \| Home Equity Line of Credit \| Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, Modified, Weighted Average Interest Rate Decrease from Modification	3.50%	3.50%
Maximum \| Home Equity Line of Credit \| Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, Modified, Weighted Average Term Increase from Modification	2 years 6 months	1 year 2 months 12 days
Maximum \| Home Equity Loan \| Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, Modified, Weighted Average Interest Rate Decrease from Modification	0.00%	0.00%
Maximum \| Home Equity Loan \| Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, Modified, Weighted Average Term Increase from Modification	0 years	0 years

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.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481933/310-10-55-12A

Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-34

Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 33
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-33

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

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

- Definition

Percentage of decrease in weighted average contractual interest rate of financing receivable modified for debtor experiencing financial difficulty.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModifiedWeightedAverageInterestRateDecreaseFromModification
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of increase in weighted average maturity of financing receivable modified for debtor experiencing financial difficulty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModifiedWeightedAverageTermIncreaseFromModification
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CollateralAxis=us-gaap_ResidentialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ContractualInterestRateReductionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=tfsl_ResidentialHomeTodayMember
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:

- Details

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

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ExtendedMaturityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: