v3.26.1
Schedule H, Line 4i- Schedule of Assets (Held at End of Year) (Detail) - EBP 022 [Member] - USD ($)
12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
EBP, Schedule of Asset Held for Investment [Line Items]    
Entity Tax Identification Number 04-2271897  
EBP, Plan Number 022  
EBP, Note Receivable from Participant $ 3,617,716 [1] $ 3,393,279
EBP, Asset Held for Investment 923,888,139  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value $ 920,270,423  
Investment, Identifier [Axis]: Cabot Corporation | Company Stock    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Cabot Corporation [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Company Stock [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 40,128,718  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: MFS Growth Equity Fund Class S | Common collective trust    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] MFS Growth Equity Fund Class S [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Common Collective Trust [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 78,774,367  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Explorer Fund | Mutual fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Explorer Fund [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Fund [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 31,460,073  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Extended Market Index Fund | Mutual fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Extended Market Index Fund [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Fund [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 42,173,888  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Federal Money Market Fund | Mutual fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Federal Money Market Fund [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Fund [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 772,359  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Inflation-Protected Securities Fund: Adm Shares | Mutual fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard InflationProtected Securities Fund Adm Shares [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Fund [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 6,474,952  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Institutional Index Fund | Mutual fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Institutional Index Fund [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Fund [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 187,678,826  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard International Growth Fund | Mutual fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard International Growth Fund [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Fund [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 31,787,218  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard International Value Fund | Mutual fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard International Value Fund [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Fund [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 9,076,017  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Retirement Savings Trust III | Common collective trust    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Retirement Savings Trust III [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Common Collective Trust [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 31,672,951  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Short-term Federal Fund | Mutual fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Shortterm Federal Fund [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Fund [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 17,810,768  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Target Retirement 2020 Trust II | Common collective trust    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Target Retirement 2020 Trust II [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Common Collective Trust [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 10,526,514  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Target Retirement 2025 Trust II | Common collective trust    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Target Retirement 2025 Trust II [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Common Collective Trust [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 12,754,099  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Target Retirement 2030 Trust II | Common collective trust    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Target Retirement 2030 Trust II [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Common Collective Trust [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 38,858,350  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Target Retirement 2035 Trust II | Common collective trust    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Target Retirement 2035 Trust II [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Common Collective Trust [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 31,540,660  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Target Retirement 2040 Trust II | Common collective trust    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Target Retirement 2040 Trust II [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Common Collective Trust [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 25,569,787  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Target Retirement 2045 Trust II | Common collective trust    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Target Retirement 2045 Trust II [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Common Collective Trust [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 30,041,639  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Target Retirement 2050 Trust II | Common collective trust    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Target Retirement 2050 Trust II [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Common Collective Trust [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 31,012,717  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Target Retirement 2055 Trust II | Common collective trust    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Target Retirement 2055 Trust II [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Common Collective Trust [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 17,130,703  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Target Retirement 2060 Trust II | Common collective trust    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Target Retirement 2060 Trust II [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Common Collective Trust [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 7,784,829  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Target Retirement 2065 Trust II | Common collective trust    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Target Retirement 2065 Trust II [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Common Collective Trust [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 3,063,372  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Target Retirement 2070 Trust II| Common collective trust    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Target Retirement 2070 Trust II [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Common Collective Trust [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 546,925  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Target Retirement Income Trust II | Common collective trust    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Target Retirement Income Trust II [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Common Collective Trust [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 8,693,862  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Target Retirement Income and Growth Trust II | Common collective trust    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Target Retirement Income and Growth Trust II [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Common Collective Trust [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 6,995  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Total Bond Market Index Fund | Mutual fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Total Bond Market Index Fund [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Fund [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 64,937,034  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Total International Bond Index Fund | Mutual fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Total International Bond Index Fund [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Fund [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 13,407,219  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Total International Stock Index Fund | Mutual fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Total International Stock Index Fund [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Fund [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 51,497,298  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Wellington Fund | Mutual fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Wellington Fund [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Fund [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 53,527,889  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Investment, Identifier [Axis]: Vanguard Windsor II Fund | Mutual fund    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Investment, Issuer Name [Extensible Enumeration] Vanguard Windsor II Fund [Member]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Fund [Member]  
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Participant-Directed [Member]  
EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value [1] $ 41,560,394  
EBP, Asset Held for Investment, Party-in-Interest [true false] [1] true  
Maximum [Member]    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Asset Held for Investment, Participant Loan, Interest Rate 10.50%  
Maximum [Member] | Investment, Identifier [Axis]: Notes Receivable from Participants    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Asset Held for Investment, Participant Loan, Interest Rate 10.50%  
Minimum [Member]    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Asset Held for Investment, Participant Loan, Interest Rate 5.25%  
Minimum [Member] | Investment, Identifier [Axis]: Notes Receivable from Participants    
EBP, Schedule of Asset Held for Investment [Line Items]    
EBP, Asset Held for Investment, Participant Loan, Interest Rate 5.25%  
[1] Indicates party-in-interest to the Plan