Long-term Debt - Schedule of 2.25% Convertible Senior Notes (Details) - 2 1/4% Notes $ / shares in Units, $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2021 USD ($) $ / shares	Sep. 30, 2020	Dec. 31, 2020 USD ($) $ / shares
Debt Instrument [Line Items]
Carrying amount of equity component, net of equity issuance costs | $	$ 0.0		$ 54.5
Remaining amortization period (years)	2 years 3 months		3 years
Effective interest rate (as a percent)	5.80%		5.80%
Common stock conversion rate (in shares per USD)	0.0384615	0.0384615
Conversion price (in USD per share) | $ / shares	$ 26.00		$ 26.00