Long-Term Debt (Tables)

12 Months Ended

Dec. 31, 2024

Text Block [Abstract]

Outstanding Long-Term Debt

Our outstanding long-term debt is shown below:

	As of December 31,
(in millions)	2024		2023
Uncollateralized senior notes:
5.68% notes, due June 2026	$	5.8	$	8.7
6.39% notes, due December 2026	100.0		100.0
6.44% notes, due December 2027	100.0		100.0
6.43% notes, due May 2028	2.8		3.5
3.73% notes, due December 2028	8.0		10.0
6.45% notes, due December 2028	100.0		100.0
3.88% notes, due May 2029	25.0		30.0
5.20% notes, due October 2029	100.0		—
6.62% notes, due December 2030	100.0		100.0
3.25% notes, due April 2032	52.5		59.5
6.71% notes, due December 2033	100.0		100.0
2.98% notes, due December 2034	70.0		70.0
3.00% notes, due July 2035	50.0		50.0
2.96% notes, due August 2035	40.0		40.0
2.49% notes, due January 2037	50.0		50.0
5.43% notes, due March 2038	80.0		80.0
3.48% notes, due May 2038	50.0		50.0
3.58% notes, due November 2038	50.0		50.0
6.73% notes, due December 2038	50.0		50.0
3.98% notes, due August 2039	100.0		100.0
2.95% notes, due March 2042	50.0		50.0
Equipment security note
2.46% note, due September 2031	6.7		7.6
Less: debt issuance costs	(3.6)		(3.7)
Total long-term debt	1,287.2		1,205.6
Less: current maturities	(25.5)		(18.5)
Total long-term debt, net of current maturities	$	1,261.7	$	1,187.1

Line of Credit Facility [Line Items]

Schedule of Line of Credit Facilities [Table Text Block]