Inventories (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Inventories
LIFO inventories - cost on FIFO method	$ 1,387.7	$ 1,737.3
Cost on FIFO method higher than LIFO value	(137.6)	(293.6)
Inventories - stated on LIFO method	1,250.1	1,443.7
Inventories - stated on FIFO method	395.6	373.4
Inventories	1,645.7	1,817.1
LIFO inventory valuation reserve adjustment (income) charge	(156.0)	$ 271.8	$ 73.3
Liquidation of LIFO inventory quantities that decreased cost of sales	$ (11.6)