Other Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Goodwill [Roll Forward]
Beginning Balance	$ 630.5
Ending Balance	631.2	$ 630.5
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	245.5	245.5
Intangible Assets, Net (Excluding Goodwill)	196.2	211.4
Amortization of Intangible Assets	15.2	14.4
Other assets
Prepaid Expense, Current	34.8	27.5
Income Taxes Receivable, Current	5.3	3.9
Other Assets, Miscellaneous, Current	12.4	6.9
Other Assets, Current	52.5	38.3
Deferred financing costs	0.9	0.9
Less: Accumulated amortization-deferred financing costs	(0.9)	(0.8)
Deferred financing costs, net	0.0	0.1
Equity in net assets of affiliates	0.8	1.1
Equity in net assets of affiliates	3.5	6.4
Restricted Cash and Investments, Noncurrent	22.3	19.6	$ 19.5	$ 19.5
Rotables	44.0	39.0
Other	29.3	25.6
Goodwill	631.2	630.5
Total	99.9	91.8
Favorable Leasehold [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	2.8	2.8
Finite-Lived Intangible Assets, Accumulated Amortization	(2.1)	(2.1)
Developed Technology
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	103.1	103.1
Finite-Lived Intangible Assets, Accumulated Amortization	(21.9)	(15.0)
Customer Contracts
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	139.6	139.6
Finite-Lived Intangible Assets, Accumulated Amortization	$ (25.3)	$ (17.0)