v3.26.1
Schedule H, Line 4i - Schedule of Assets (Held at End of Year) (Details) - EBP 002 - USD ($)
12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
EBP, Schedule of Asset Held for Investment [Line Items]    
Entity tax identification number 22-0900560  
Plan number 002  
Asset held for investment, participant loan, after deemed distribution $ 398,878  
Total assets held $ 157,464,796  
Minimum    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, participant loan, interest rate 4.00% 4.00%
Maximum    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, participant loan, interest rate 10.50% 10.50%
Mutual funds    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value $ 148,240,833  
Investment, Identifier [Axis]: Columbia Financial, Inc. | Employer Common Stock    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 8,825,085  
Investment, Identifier [Axis]: Mutual Funds | AB | AB Small Cap Growth    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 1,135,022  
Investment, Identifier [Axis]: Mutual Funds | Calvert | Calvert Bond Fund A    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 658,374  
Investment, Identifier [Axis]: Mutual Funds | Calvert | Calvert International    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 145,028  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Extended Market Index    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 2,902,086  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity 500 Index    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 12,244,426  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Balanced    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 6,318,927  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Blue Chip Growth    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 15,129,562  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Capital & Income    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 1,553,824  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Capital Appreciation    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 5,461,880  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Diversified International K6    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 2,744,932  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Equity-Income    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 4,514,257  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Freedom 2010    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 260,495  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Freedom 2015    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 170,378  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Freedom 2020    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 5,689,712  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Freedom 2025    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 7,006,738  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Freedom 2030    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 8,477,731  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Freedom 2035    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 5,842,786  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Freedom 2040    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 5,928,900  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Freedom 2045    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 5,056,453  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Freedom 2050    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 5,427,484  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Freedom 2055    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 4,052,631  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Freedom 2060    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 3,832,402  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Freedom 2065    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 799,517  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Freedom 2070    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 36,243  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Freedom Income    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 426,240  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity GNMA    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 441,453  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Growth Company    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 15,258,468  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity Large Growth    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 2,293,097  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity OTC Portfolio    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 9,586,958  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Fidelity U.S. Bond Index    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 2,033,391  
Investment, Identifier [Axis]: Mutual Funds | Fidelity | Global Ex U.S. Index    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 1,055,331  
Investment, Identifier [Axis]: Mutual Funds | John Hancock | John Hancock Mid Cap    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 651,727  
Investment, Identifier [Axis]: Mutual Funds | Parnassus | Parnassus Core Equity    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 49,587  
Investment, Identifier [Axis]: Mutual Funds | Pimco | Pimco Real Return Instl    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 631,482  
Investment, Identifier [Axis]: Mutual Funds | Royce | Royce Small Cap Instl    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 1,224,431  
Investment, Identifier [Axis]: Mutual Funds | Vanguard | Vanguard Federal Money Market    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value 8,531,314  
Investment, Identifier [Axis]: Mutual Funds | Vanguard | Vanguard LT Treasury    
EBP, Schedule of Asset Held for Investment [Line Items]    
Asset held for investment, investment, excluding plan interest in master trust, current value $ 667,566