Summary of Significant Accounting Policies (Activity in the LIFO Reserve) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019
LIFO Reserve [Roll Forward]
Balance, beginning of year	$ 82.2	$ 50.9	$ 33.8
LIFO (benefit) expense	(32.3)	31.3	18.6
Allocated to divested businesses	0.0	0.0	(1.5)
Balance, end of year	$ 82.2	$ 50.9	$ 33.8	$ 49.9