v3.26.1
Fair Value of Financial Instruments - Summary of Changes in Fair Value of Investments (Detail) - USD ($)
$ in Millions
Mar. 31, 2026
Dec. 31, 2025
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Investments, at fair value $ 16.4 $ 17.2
Energy Marketing Contract Liabilities, Current 0.2 0.8
Energy Marketing Contract Liabilities, Total [1] 0.7 1.4
Energy Marketing Contracts Assets, Total [2] 0.9 0.0
Quoted Prices in Active Markets (Level 1) [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Assets, Fair Value Disclosure 15.6 16.3
Fair Value, Inputs, Level 2 [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Assets, Fair Value Disclosure 0.9 0.0
Significant Unobservable Inputs (Level 3) [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Assets, Fair Value Disclosure 0.8 0.9
Recurring [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Assets, Fair Value Disclosure 17.3 17.2
Energy Marketing Contract Liabilities, Current   1.4
Investments in guaranteed income fund [Member] | Significant Unobservable Inputs (Level 3) [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Investments, at fair value 0.8 0.9
Investments in guaranteed income fund [Member] | Recurring [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Investments, at fair value 0.8 0.9
Total Investments [Member] | Quoted Prices in Active Markets (Level 1) [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Investments, at fair value 15.6  
Total Investments [Member] | Significant Unobservable Inputs (Level 3) [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Investments, at fair value 0.8  
Total Investments [Member] | Recurring [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Investments, at fair value 16.4  
Mark To Market Energy Assets Including Put Option [Member] | Recurring [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Derivative Asset 0.9  
Other Investments | Quoted Prices in Active Markets (Level 1) [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Investments, at fair value $ 15.6 16.3
Other Investments | Recurring [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Investments, at fair value   $ 16.3
[1]
(1) Derivative liabilities, at fair value, include $0.2 million in current liabilities in the condensed consolidated balance sheet at March 31, 2026 and $0.8 million at December 31, 2025, with the remainder of the balances classified as long-term.
[2]
 (1) Derivative assets, at fair value, include $0.8 million in current assets in the condensed consolidated balance sheet at March 31, 2026, with the remainder of the balances classified as long-term. There were no current derivative asset at December 31, 2025,