Derivatives and Fair Value Measurements - Fair Value of Long-term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Fair Value of Debt [Line Items]
Total debt at par value	$ 333.8	$ 1,137.8
Carrying Amount
Fair Value of Debt [Line Items]
Total debt at par value	343.6	1,173.2
Less: Unamortized debt issuance costs and original issue discount	(9.8)	(35.4)
Net carrying amount	333.8	1,137.8
Estimated Fair Value
Fair Value of Debt [Line Items]
Estimated fair value	$ 560.0	$ 1,136.5

[Line Items] for Fair Value of Debt [Table]

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- Definition

Amount of short-term and long-term debt and lease obligation.

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- Definition

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Amount of long-term debt and lease obligation, including portion classified as current.

+ References

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- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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