General - Stock Compensation - Stock Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Stock Compensation
Stock compensation expense	$ 6.0	$ 5.8	$ 19.4	$ 18.8
Stock compensation expense, discontinued operations		$ 0.4		$ 1.0
Minimum
Stock Compensation
Estimated forfeitures (as a percent)	0.00%	0.00%	0.00%	0.00%
Maximum
Stock Compensation
Estimated forfeitures (as a percent)	4.00%	4.00%	4.00%	4.00%