Stock Plans - Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Stock Plans
Compensation cost on stock-based compensation plans	$ 3.7	$ 3.1	$ 7.4	$ 5.7