v3.25.4
Fair Value (Tables)
 12 Months Ended
Dec. 31, 2025
Fair Value Disclosures [Abstract]  
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis
The following tables present financial assets and liabilities measured and recorded at fair value on our Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of December 31, 2025 and December 31, 2024. As of December 31, 2025 and December 31, 2024, there were no material transfers between fair value hierarchies. Additionally, there were no changes in the method or significant assumptions used to estimate the fair value of our financial instruments.
Recurring Fair Value Measurements
December 31, 2025 (in millions)
Quoted Prices
in Active Markets
for Identical Assets
(Level 1)		Significant Other
Observable Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)
Balance as of
December 31, 2025
Assets
Risk management assets$— $18.8 $— $18.8 
Available-for-sale debt securities— 146.1 — 146.1 
Equity Securities(1)(2)
8.5 — — 8.5 
Total$8.5 $164.9 $— $173.4 
Liabilities
Risk management liabilities$— $5.9 $— $5.9 
Total$— $5.9 $— $5.9 
(1) Equity securities are in a high dividend equity fund and are valued using market prices in active markets. Level 1 instrument valuations are obtained from real-time quotes for transactions in active exchange markets involving identical assets. Equity securities are presented in "Other Investments" on the Consolidated Balance Sheets.
(2)As of December 31, 2025, the investment cost of equity securities measured at fair value was $7.9 million, gross unrealized gains were $0.7 million, and the fair value was $8.5 million.

Recurring Fair Value Measurements
December 31, 2024 (in millions)
Quoted Prices
in Active Markets
for Identical Assets
(Level 1)		Significant Other
Observable Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)
Balance as of
December 31, 2024
Assets
U.S. Treasury debt securities(1)
$80.1 $— $— $80.1 
Risk management assets— 27.0 — 27.0 
Available-for-sale debt securities— 86.7 — 86.7 
Total$80.1 $113.7 $— $193.8 
Liabilities
Risk management liabilities$— $3.5 $— $3.5 
Total$— $3.5 $— $3.5 
(1)Treasury bills are presented in "Cash and cash equivalents" and "Restricted cash" on the Consolidated Balance Sheets.
Debt Securities, Available-for-sale
The amortized cost, gross unrealized gains and losses, allowance for credit losses, and fair value of available-for-sale securities at December 31, 2025 and 2024 were: 
December 31, 2025 (in millions)
Amortized
Cost		Gross
Unrealized
Gains
Gross
Unrealized
Losses(1)
Allowance for Credit LossesFair Value
Available-for-sale debt securities
U.S. Treasury debt securities$9.5 $— $— $— $9.5 
Corporate/Other debt securities136.3 2.4 (2.1)— 136.6 
Total$145.8 $2.4 $(2.1)$— $146.1 
December 31, 2024 (in millions)
Amortized
Cost		Gross
Unrealized
Gains
Gross
Unrealized
Losses(2)
Allowance for Credit LossesFair Value
Available-for-sale debt securities
Corporate/Other debt securities91.9 0.5 (5.6)(0.1)86.7 
Total$91.9 $0.5 $(5.6)$(0.1)$86.7 
(1) Fair value of U.S. Treasury debt securities and Corporate/Other debt securities in an unrealized loss position without an allowance for credit losses is $3.5 million and $40.2 million, respectively at December 31, 2025.
(2) Fair value of Corporate/Other debt securities in an unrealized loss position without an allowance for credit losses is $70.1 million at December 31, 2024.
Carrying Amount And Estimated Fair Values Of Financial Instruments
The carrying amount and estimated fair values of these financial instruments were as follows: 
At December 31, (in millions)
Carrying
Amount
2025
Estimated
Fair Value
2025
Carrying
Amount
2024
Estimated
Fair Value
2024
Long-term debt (including current portion)$15,477.5 $14,975.3 $13,355.7 $12,505.2