Summary of Significant Accounting Policies - Financial Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Reported Value Measurement | 4.875% senior notes due 2030
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed-rate debt	$ 400.0	$ 400.0
Level 2 | Estimate of Fair Value Measurement | 4.875% senior notes due 2030
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed-rate debt	385.0	374.5
Money Market Funds | Fair Value, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value	$ 721.2	$ 899.4