v3.25.2
Fair Value (Tables)
 6 Months Ended
Jun. 30, 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 Condensed Consolidated Balance Sheets (unaudited) on a recurring basis and their level within the fair value hierarchy as of June 30, 2025 and December 31, 2024:
Recurring Fair Value Measurements
June 30, 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
June 30, 2025
Assets
U.S. Treasury debt securities(1)
$1.5 $— $— $1.5 
Risk management assets— 36.9 — 36.9 
Available-for-sale debt securities— 144.9 — 144.9 
Equity securities(2)(3)
$6.1 $— $— $6.1 
Total$7.6 $181.8 $— $189.4 
Liabilities
Risk management liabilities$— $5.5 $— $5.5 
Total$— $5.5 $— $5.5 
(1)Treasury bills are presented in "Cash and cash equivalents" and "Restricted cash" on the Consolidated Balance Sheets.
(2)Equity securities 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.
(3)As of June 30, 2025, the investment cost of equity securities was $5.9 million, gross unrealized gains were $0.2 million, and the fair value was $6.1 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 
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 June 30, 2025 and December 31, 2024 were: 
June 30, 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 securities4.3 $— $— $— $4.3 
Corporate/Other debt securities$143.6 $1.4 $(4.3)$(0.1)$140.6 
Total$147.9 $1.4 $(4.3)$(0.1)$144.9 
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 securities$91.9 $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 $2.7 million and $61.6 million at June 30, 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: 
(in millions)
Carrying
Amount as of
June 30, 2025
Estimated Fair
Value as of
June 30, 2025
Carrying
Amount as of
Dec. 31, 2024
Estimated Fair
Value as of
Dec. 31, 2024
Long-term debt (including current portion)$15,756.0 $15,106.3 $13,355.7 $12,505.2