Supplemental Information (Expenses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of expenses in statements of operations
Research and development	$ 69.9	$ 72.2	$ 73.6
Advertising, promotions and marketing	43.7	42.5	45.0
Cooperative advertising expenditures	$ 21.3	$ 16.8	$ 18.6