Long-Term Debt - 2 1/4% Convertible Senior Notes (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) $ / shares	Dec. 31, 2020 USD ($) $ / shares	Mar. 10, 2021 $ / shares	Dec. 20, 2020 $ / shares
Debt Instrument [Line Items]
Carrying value	$ 136.5	$ 271.6
Principal amount	428.1	608.5
Conversion price per share (in USD per share) | $ / shares			$ 51.00	$ 56.00
2 1/4% Notes
Debt Instrument [Line Items]
Carrying value	136.5	271.6
Unamortized discount and deferred financing costs	9.4	28.4
Principal amount	145.9	300.0
Carrying amount of equity component, net of equity issuance costs	$ 0.0	$ 54.5
Remaining amortization period (years)	2 years	3 years
Effective interest rate (percentage)	5.80%	5.80%
Common stock conversion rate (in shares per USD)	0.0384615
Conversion price per share (in USD per share) | $ / shares	$ 26.00	$ 26.00