v3.26.1
Employee Benefit Plan, Fair Value and NAV (Details) - EBP Third Federal 401(k) Savings Plan - USD ($)
 3 Months Ended
Dec. 31, 2025
Dec. 31, 2024
EBP, Investment, Fair Value and NAV [Abstract]    
EBP, Investment, Accumulated Gain (Loss) $ 26,036,841 $ 20,591,323
EBP, Investment, Increase from Interest and Dividend Income on Investment 3,312,573 2,838,434
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Accumulated Gain (Loss) 26,036,841 20,591,323
EBP, Investment, Increase from Interest and Dividend Income on Investment 3,312,573 2,838,434
EBP, Investment, Fair Value 220,977,254 199,750,476
Valuation, Market and Cost Approach    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 109,164,218 98,398,352
Fair Value, Inputs, Level 1    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 96,371,269 85,250,024
Fair Value, Inputs, Level 1 | Valuation, Market and Cost Approach    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 96,371,269 85,250,024
Fair Value, Inputs, Level 2    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 12,792,949 13,148,328
Fair Value, Inputs, Level 2 | Valuation, Market and Cost Approach    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 12,792,949 13,148,328
Fair Value, Inputs, Level 3    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 0 0
Fair Value, Inputs, Level 3 | Valuation, Market and Cost Approach    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 0 0
Common Stock    
EBP, Investment, Fair Value and NAV [Abstract]    
EBP, Investment, Accumulated Gain (Loss) 973,202 2,345,753
EBP, Investment, Increase from Dividend Income on Investment 1,330,222 1,278,179
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Accumulated Gain (Loss) 973,202 2,345,753
EBP, Investment, Increase from Dividend Income on Investment 1,330,222 1,278,179
Certificates of Deposit    
EBP, Investment, Fair Value and NAV [Abstract]    
EBP, Investment, Increase from Interest Income on Investment 382,487 327,588
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Increase from Interest Income on Investment 382,487 327,588
Certificates of Deposit | Valuation, Cost Approach    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 12,792,949 13,148,328
Certificates of Deposit | Fair Value, Inputs, Level 1 | Valuation, Cost Approach    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 0 0
Certificates of Deposit | Fair Value, Inputs, Level 2 | Valuation, Cost Approach    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 12,792,949 13,148,328
Certificates of Deposit | Fair Value, Inputs, Level 3 | Valuation, Cost Approach    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 0 0
Other Investment Companies | Valuation, Market Approach    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 81,537,063 70,887,863
Other Investment Companies | Fair Value, Inputs, Level 1 | Valuation, Market Approach    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 81,537,063 70,887,863
Other Investment Companies | Fair Value, Inputs, Level 2 | Valuation, Market Approach    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 0 0
Other Investment Companies | Fair Value, Inputs, Level 3 | Valuation, Market Approach    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 0 0
EBP, Employer, Common Stock    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 14,834,206 14,362,161
EBP, Employer, Common Stock | Valuation, Market Approach    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 14,834,206 14,362,161
EBP, Employer, Common Stock | Fair Value, Inputs, Level 1 | Valuation, Market Approach    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 14,834,206 14,362,161
EBP, Employer, Common Stock | Fair Value, Inputs, Level 2 | Valuation, Market Approach    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 0 0
EBP, Employer, Common Stock | Fair Value, Inputs, Level 3 | Valuation, Market Approach    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 0 0
EBP, Pooled Separate Account    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 111,813,036 101,352,124
EBP, Pooled Separate Account | Fair Value, Inputs, Level 1    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 0 0
EBP, Pooled Separate Account | Fair Value, Inputs, Level 2    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value 0 0
EBP, Pooled Separate Account | Fair Value, Inputs, Level 3    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, Fair Value $ 0 $ 0