v3.24.3
Fair Value (Tables)
 9 Months Ended
Sep. 30, 2024
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 September 30, 2024 and December 31, 2023:
Recurring Fair Value Measurements
September 30, 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
September 30, 2024
Assets
Risk management assets$— $18.9 $— $18.9 
Available-for-sale debt securities— 137.9 — 137.9 
Total$— $156.8 $— $156.8 
Liabilities
Risk management liabilities$— $6.7 $— $6.7 
Total$— $6.7 $— $6.7 
Recurring Fair Value Measurements
December 31, 2023 (in millions)
Quoted Prices in
Active Markets
for Identical
Assets
(Level 1)		Significant
Other
Observable
Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)
Balance as of
December 31, 2023
Assets
Risk management assets$— $23.3 $— $23.3 
Available-for-sale debt securities— 159.1 — 159.1 
Total$— $182.4 $— $182.4 
Liabilities
Risk management liabilities$— $9.4 $— $9.4 
Total$— $9.4 $— $9.4 
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 September 30, 2024 and December 31, 2023 were: 
September 30, 2024 (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$49.1 $— $(1.9)$— $47.2 
Corporate/Other debt securities94.4 1.1 (4.6)(0.2)90.7 
Total$143.5 $1.1 $(6.5)$(0.2)$137.9 
December 31, 2023 (in millions)
Amortized
Cost		Gross Unrealized Gains
Gross Unrealized Losses(2)
Allowance for Credit LossesFair
Value
Available-for-sale debt securities
U.S. Treasury debt securities$63.8 $— $(3.2)$— $60.6 
Corporate/Other debt securities105.2 0.8 (6.9)(0.6)98.5 
Total$169.0 $0.8 $(10.1)$(0.6)$159.1 
(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 $41.2 million and $66.5 million, respectively, at September 30, 2024.
(2)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 $58.7 million and $74.8 million, respectively, at December 31, 2023.
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
September 30, 2024
Estimated Fair
Value as of
September 30, 2024
Carrying
Amount as of
Dec. 31, 2023
Estimated Fair
Value as of
Dec. 31, 2023
Long-term debt (including current portion)$13,357.5 $12,926.5 $11,079.3 $10,370.9