Long-Term Debt - Interest Expense Components for the 2¼% Notes (Details) - 2 1/4% Notes - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Debt Instrument [Line Items]
Interest expense-contractual interest	$ 0.7	$ 0.8	$ 2.3	$ 2.4
Interest expense-amortization of debt discount (see discussion above)	0.0	1.0	0.0	3.2
Interest expense-amortization of deferred financing costs	$ 0.1	$ 0.1	$ 0.3	$ 0.3