v3.26.1
SCHEDULE H, LINE 4i – SCHEDULE OF ASSETS (HELD AT END OF YEAR) (Details) - EBP 004
12 Months Ended
Dec. 31, 2025
USD ($)
EBP, Schedule of Asset Held for Investment [Line Items]  
Entity tax identification number 36-1063330
Plan number 004
Current value $ 615,052,191
Participants’ loans 8,583,777
Total assets held at end of year $ 623,635,968
Minimum  
EBP, Schedule of Asset Held for Investment [Line Items]  
Loan interest rate 4.25%
Maximum  
EBP, Schedule of Asset Held for Investment [Line Items]  
Loan interest rate 9.50%
Investment, Identifier [Axis]: DFA Emerging Markets Core Equity Portfolio Institutional Class | Mutual fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value $ 1,272,382
Investment, Identifier [Axis]: Dodge & Cox Income Fund Class X | Mutual fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 3,330,345
Investment, Identifier [Axis]: Federal Signal Stock Fund | Common stock fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 62,318,090
Investment, Identifier [Axis]: Vanguard Cash Reserve Federal Money Market Fund | Mutual fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 273,361
Investment, Identifier [Axis]: Vanguard Explorer Fund | Mutual fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 19,118,728
Investment, Identifier [Axis]: Vanguard Institutional Index Fund | Mutual fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 70,645,562
Investment, Identifier [Axis]: Vanguard Institutional Target Retirement 2020 Trust II | Common/collective trust  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 8,893,927
Investment, Identifier [Axis]: Vanguard Institutional Target Retirement 2025 Trust II | Common/collective trust  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 34,315,285
Investment, Identifier [Axis]: Vanguard Institutional Target Retirement 2030 Trust II | Common/collective trust  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 50,113,968
Investment, Identifier [Axis]: Vanguard Institutional Target Retirement 2035 Trust II | Common/collective trust  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 40,347,060
Investment, Identifier [Axis]: Vanguard Institutional Target Retirement 2040 Trust II | Common/collective trust  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 34,300,338
Investment, Identifier [Axis]: Vanguard Institutional Target Retirement 2045 Trust II | Common/collective trust  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 37,308,592
Investment, Identifier [Axis]: Vanguard Institutional Target Retirement 2050 Trust II | Common/collective trust  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 26,985,851
Investment, Identifier [Axis]: Vanguard Institutional Target Retirement 2055 Trust II | Common/collective trust  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 17,469,484
Investment, Identifier [Axis]: Vanguard Institutional Target Retirement 2060 Trust II | Common/collective trust  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 12,997,197
Investment, Identifier [Axis]: Vanguard Institutional Target Retirement 2065 Trust II | Common/collective trust  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 7,735,330
Investment, Identifier [Axis]: Vanguard Institutional Target Retirement 2070 Trust II | Common/collective trust  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 2,368,579
Investment, Identifier [Axis]: Vanguard Institutional Target Retirement Income Trust II | Common/collective trust  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 7,706,402
Investment, Identifier [Axis]: Vanguard International Growth Fund | Mutual fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 13,169,578
Investment, Identifier [Axis]: Vanguard Mid-Cap Index Fund Admiral Shares | Mutual fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 4,122,906
Investment, Identifier [Axis]: Vanguard PRIMECAP Fund | Mutual fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 92,741,963
Investment, Identifier [Axis]: Vanguard Retirement Savings Trust III | Common/collective trust  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 41,096,027
Investment, Identifier [Axis]: Vanguard Small-Cap Value Index Fund | Mutual fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value 10,811,722
Investment, Identifier [Axis]: Vanguard Total Bond Market Index Fund | Mutual fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
Current value $ 15,609,514