Significant Accounting Policies - Impact on Financial Statements (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2021	Dec. 31, 2020
Liabilities
Accrued income taxes	$ 3.5	$ 16.1		$ 46.5
Current convertible notes	256.9	255.9		220.9
Long-term deferred tax liabilities	46.1	59.8		60.2
Equity
Additional paid-in capital	1,850.2	779.0		780.8
Retained earnings	902.2	878.2		808.4
Unamortized discount	29.9	0.0
Unamortized debt issuance costs	4.8	0.0
Convertible Notes, due 2024 | Convertible Debt
Equity
Unamortized discount				34.8
Unamortized debt issuance costs	$ 1.9	$ 2.9	$ 3.9	3.1
Cumulative effect of accounting change
Liabilities
Accrued income taxes				(0.2)
Current convertible notes				34.0
Long-term deferred tax liabilities				(7.6)
Equity
Additional paid-in capital				(36.9)
Retained earnings				10.7
Cumulative Effect, Period of Adoption, Adjusted Balance
Liabilities
Accrued income taxes				46.3
Current convertible notes				254.9
Long-term deferred tax liabilities				52.6
Equity
Additional paid-in capital				743.9
Retained earnings				$ 819.1