Fair Value Measurements - Assets and Liabilities Measured on Recurring Basis (Details) - Fair Value, Recurring - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 423.5	$ 865.2
Restricted cash	170.1	119.4
Short-term investment securities	117.1	112.5
Total assets	710.7	1,097.1
Derivative liability		11.1
Total liabilities	0.0	11.1
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	423.5	865.2
Restricted cash	170.1	119.4
Short-term investment securities	117.1	112.5
Total assets	710.7	1,097.1
Derivative liability		0.0
Total liabilities	0.0	0.0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0.0	0.0
Restricted cash	0.0	0.0
Short-term investment securities	0.0	0.0
Total assets	0.0	0.0
Derivative liability		11.1
Total liabilities	0.0	11.1
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0.0	0.0
Restricted cash	0.0	0.0
Short-term investment securities	0.0	0.0
Total assets	0.0	0.0
Derivative liability		0.0
Total liabilities	$ 0.0	$ 0.0