v3.25.4
Pension Plans and Postretirement Benefits - Summary of Total Investments Measured at Fair Value (Detail) - USD ($)
$ in Thousands
Dec. 31, 2025
Dec. 31, 2024
Fair Value, Separate Account Investment [Line Items]    
Total Assets $ 1,369,558 $ 865,552
Unclassified 853,387 525,358
U.S. Government Securities    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 187,854 261,008
Unclassified 0 0
Commingled and Mutual Funds    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 280,517 231,292
Unclassified 269,808 188,383
Real Estate    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 125,031 110,223
Unclassified 125,031 110,223
Diversified Credit    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 105,421 111,003
Unclassified 105,421 111,003
Fixed Income    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 514,772 107,287
Unclassified 197,164 71,010
Partnerships with Security Holdings    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 99,933 14,348
Unclassified 99,933 14,348
Cash and Accrued Items    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 56,030 30,391
Unclassified 56,030 30,391
Level 1    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 516,171 340,194
Level 1 | U.S. Government Securities    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 187,854 261,008
Level 1 | Commingled and Mutual Funds    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 10,709 42,909
Level 1 | Real Estate    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 1 | Diversified Credit    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 1 | Fixed Income    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 317,608 36,277
Level 1 | Partnerships with Security Holdings    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 1 | Cash and Accrued Items    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 2    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 2 | U.S. Government Securities    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 2 | Commingled and Mutual Funds    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 2 | Real Estate    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 2 | Diversified Credit    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 2 | Fixed Income    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 2 | Partnerships with Security Holdings    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 2 | Cash and Accrued Items    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 3    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 3 | U.S. Government Securities    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 3 | Commingled and Mutual Funds    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 3 | Real Estate    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 3 | Diversified Credit    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 3 | Fixed Income    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 3 | Partnerships with Security Holdings    
Fair Value, Separate Account Investment [Line Items]    
Total Assets 0 0
Level 3 | Cash and Accrued Items    
Fair Value, Separate Account Investment [Line Items]    
Total Assets $ 0 $ 0