Acquisition - Pro Forma Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Actual sales and earnings
Net sales	$ 1,185.8	$ 1,047.7
Net earnings	174.3	134.2
Manufacturers Supply Company
Business Acquisition [Line Items]
Net sales		13.5
Net earnings		$ 1.6
Actual sales and earnings
Net sales	13.6
Net earnings	$ 1.3