Derivatives and Fair Value Measurements - Long-term debt (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Carrying amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total debt at par value	$ 342.1	$ 343.6
Net carrying amount	333.6	333.8
Estimated fair value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated fair value	506.2	560.0
Less: Unamortized debt issuance costs	(8.5)	(9.8)
Net carrying amount	$ 333.6	$ 333.8

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, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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

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