The following tables summarizes the fair value hierarchy for each type of instrument carried at fair value on a recurring basis (in millions): | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Fair Value Measurements at June 30, 2026 Using | | | Total Carrying Value at June 30, 2026 | | Quoted Prices in Active Market
(Level One) | | Significant Other Observable Inputs
(Level Two) | | Significant Unobservable Inputs
(Level Three) | | Asset Class: | | | | | | | | | Mutual fund investments in a non-qualified savings plan(a)(b) | | $ | 4.1 | | | $ | 4.1 | | | $ | — | | | $ | — | | | Derivatives – natural gas instruments, net | | 4.7 | | | — | | | 4.7 | | | — | | | Total assets at fair value | | $ | 8.8 | | | $ | 4.1 | | | $ | 4.7 | | | $ | — | | | Liability Class: | | | | | | | | | | Liabilities related to non-qualified savings plan | | $ | 4.1 | | | $ | 4.1 | | | $ | — | | | $ | — | | | Derivatives – natural gas instruments, net | | 5.9 | | | — | | | 5.9 | | | — | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Total liabilities at fair value | | $ | 10.0 | | | $ | 4.1 | | | $ | 5.9 | | | $ | — | |
(a)Includes mutual fund investments of approximately 37% in common stock of large-cap U.S. companies, 4% in common stock of small to mid-cap U.S. companies, 1% in the common stock of international companies, 9% in bond funds, 12% in short-term investments, and 37% in blended funds. (b)The investments related to a non-qualified deferred compensation arrangement on behalf of certain members of management. The Company has a liability for the related-party transaction recorded on Other noncurrent liabilities for deferred compensation obligation. | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Fair Value Measurements at September 30, 2025 Using | | | Total Carrying Value at
September 30, 2025 | | Quoted Prices in Active Market
(Level One) | | Significant Other Observable Inputs
(Level Two) | | Significant Unobservable Inputs
(Level Three) | | Asset Class: | | | | | | | | | Mutual fund investments in a non-qualified savings plan(a)(b) | | $ | 3.5 | | | $ | 3.5 | | | $ | — | | | $ | — | | | Derivatives – natural gas instruments, net | | 7.9 | | | — | | | 7.9 | | | — | | | Total assets at fair value | | $ | 11.4 | | | $ | 3.5 | | | $ | 7.9 | | | $ | — | | | Liability Class: | | | | | | | | | | Liabilities related to non-qualified savings plan | | $ | 3.5 | | | $ | 3.5 | | | $ | — | | | $ | — | | | Derivatives – natural gas instruments, net | | 8.7 | | | — | | | 8.7 | | | — | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Total liabilities at fair value | | $ | 12.2 | | | $ | 3.5 | | | $ | 8.7 | | | $ | — | |
(a)Includes mutual fund investments of approximately 29% in common stock of large-cap U.S. companies, 4% in common stock of small to mid-cap U.S. companies, 2% in the common stock of international companies, 9% in bond funds, 20% in short-term investments, and 36% in blended funds. (b)The investments related to a non-qualified deferred compensation arrangement on behalf of certain members of management. The Company has a liability for the related-party transaction recorded on Other noncurrent liabilities for deferred compensation obligation. The Company is required to disclose the fair value of financial instruments that are not recognized at fair value in the statement of financial position for which it is practicable to estimate that value (in millions):
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Fair Value Measurements at June 30, 2026 Using | | | Total Carrying Value at June 30, 2026 | | Quoted Prices in Active Market
(Level One) | | Significant Other Observable Inputs
(Level Two) | | Significant Unobservable Inputs
(Level Three) | 8.00% Senior Notes due July 2030 | | $ | 650.0 | | | $ | — | | | $ | 684.2 | | | $ | — | |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Fair Value Measurements at September 30, 2025 Using | | | Total Carrying Value at
September 30, 2025 | | Quoted Prices in Active Market
(Level One) | | Significant Other Observable Inputs
(Level Two) | | Significant Unobservable Inputs
(Level Three) | 8.00% Senior Notes due July 2030 | | $ | 650.0 | | | $ | — | | | $ | 680.1 | | | $ | — | | 6.75% Senior Notes due December 2027 | | 150.0 | | | — | | | 150.1 | | | — | |
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