v3.26.1
Schedule H, line 4i – Schedule of Assets (Held at End of Year) (Details) - EBP 002
12 Months Ended
Dec. 31, 2025
USD ($)
EBP, Schedule of Asset Held for Investment [Line Items]  
Tax identification number 43-1265338
Plan number 002
Participant loans $ 2,110,331
Total assets held for investment $ 139,606,754
Minimum  
EBP, Schedule of Asset Held for Investment [Line Items]  
Participant loans, interest rate 5.00%
Maximum  
EBP, Schedule of Asset Held for Investment [Line Items]  
Participant loans, interest rate 10.50%
Investment, Identifier [Axis]: Cass Information Systems, Inc. | Employer Common Stock  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value $ 617,038
Investment, Identifier [Axis]: Collective Trust Funds | Principal Global Investors Trust Company | Principal Income Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 2,362,661
Investment, Identifier [Axis]: Collective Trust Funds | Principal Global Investors Trust Company | Principal Lifetime Hybrid 2015 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 150,404
Investment, Identifier [Axis]: Collective Trust Funds | Principal Global Investors Trust Company | Principal Lifetime Hybrid 2020 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 3,124,086
Investment, Identifier [Axis]: Collective Trust Funds | Principal Global Investors Trust Company | Principal Lifetime Hybrid 2025 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 2,055,508
Investment, Identifier [Axis]: Collective Trust Funds | Principal Global Investors Trust Company | Principal Lifetime Hybrid 2030 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 17,611,522
Investment, Identifier [Axis]: Collective Trust Funds | Principal Global Investors Trust Company | Principal Lifetime Hybrid 2035 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 11,947,542
Investment, Identifier [Axis]: Collective Trust Funds | Principal Global Investors Trust Company | Principal Lifetime Hybrid 2040 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 15,021,219
Investment, Identifier [Axis]: Collective Trust Funds | Principal Global Investors Trust Company | Principal Lifetime Hybrid 2045 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 5,003,007
Investment, Identifier [Axis]: Collective Trust Funds | Principal Global Investors Trust Company | Principal Lifetime Hybrid 2050 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 13,575,494
Investment, Identifier [Axis]: Collective Trust Funds | Principal Global Investors Trust Company | Principal Lifetime Hybrid 2055 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 3,597,529
Investment, Identifier [Axis]: Collective Trust Funds | Principal Global Investors Trust Company | Principal Lifetime Hybrid 2060 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 3,279,480
Investment, Identifier [Axis]: Collective Trust Funds | Principal Global Investors Trust Company | Principal Lifetime Hybrid 2065 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 1,182,630
Investment, Identifier [Axis]: Collective Trust Funds | Principal Global Investors Trust Company | Principal Lifetime Hybrid 2070 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 40,712
Investment, Identifier [Axis]: Collective Trust Funds | Principal Global Investors Trust Company | Principal Stable Value Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 6,540,369
Investment, Identifier [Axis]: Mutual Funds | Blackrock | Blackrock Inflation Protected Bond Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 460,773
Investment, Identifier [Axis]: Mutual Funds | Fidelity Investments | Fidelity 500 Index Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 18,307,568
Investment, Identifier [Axis]: Mutual Funds | Fidelity Investments | Fidelity Extended Market Index Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 10,086,431
Investment, Identifier [Axis]: Mutual Funds | Fidelity Investments | Fidelity Total International Index Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 3,719,094
Investment, Identifier [Axis]: Mutual Funds | JP Morgan Funds | JP Morgan Equity Income Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 1,401,302
Investment, Identifier [Axis]: Mutual Funds | MFS Investment Management | MFS Growth Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 7,835,057
Investment, Identifier [Axis]: Mutual Funds | Vanguard Group | International Growth Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 1,796,672
Investment, Identifier [Axis]: Mutual Funds | Vanguard Group | Vanguard Total Bond Market Index Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 2,619,273
Investment, Identifier [Axis]: Pooled Separate Accounts | Principal Life Insurance Company | Core Plus Bond Account  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 2,355,287
Investment, Identifier [Axis]: Pooled Separate Accounts | Principal Life Insurance Company | Principal S&P 600 Index Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 1,802,479
Investment, Identifier [Axis]: Pooled Separate Accounts | Principal Life Insurance Company | Real Estate  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value 175,556
Investment, Identifier [Axis]: Pooled Separate Accounts | Principal Life Insurance Company | U.S. Property Account  
EBP, Schedule of Asset Held for Investment [Line Items]  
Assets held for investment, current value $ 827,730