v3.26.1
Stockholder's Equity - Accumulated Other Comprehensive Income (Loss) - Reclassifications of Accumulated Other Comprehensive Loss (Detail) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Amortization of pension and postretirement items:    
Tax benefit $ (21,400) $ (18,400)
Derivative, Gain (Loss) on Derivative, Net (100) 800
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan 5,100 19,800
Propane Swap Agreement [Member]    
Amortization of pension and postretirement items:    
Derivative, Gain (Loss) on Derivative, Net (100) 700
Interest Rate Swap [Member] | Derivatives designated as hedging instrument [Member]    
Amortization of pension and postretirement items:    
Derivative, Gain (Loss) on Derivative, Net $ 0 $ 100