Acquisition - Pro Forma Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Actual sales and earnings
Net sales	$ 1,121.5	$ 1,014.3	$ 2,169.2	$ 2,001.0
Net earnings	148.9	131.5	283.1	257.7
Manufacturers Supply Company [Member]
Business Acquisition [Line Items]
Net sales		12.8	27.0	24.0
Net earnings		$ 1.3	$ 3.2	$ 2.5
Actual sales and earnings
Net sales	13.5
Net earnings	$ 1.6