Supplemental Balance Sheet Information - Accounts Receivable (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts receivable	$ 121.3		$ 121.3		$ 113.2
Income tax receivable	11.6		11.6		59.3
Provision (benefit) for doubtful accounts	(0.1)	$ 0.3	(0.5)	$ 1.2
Doubtful accounts
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Allowances and doubtful accounts	(3.5)		(3.5)		(4.4)
Sales discounts
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Allowances and doubtful accounts	(0.3)		(0.3)		(0.2)
Accounts receivable, net of allowances	$ 129.1		$ 129.1		$ 167.9