Acquisition and Discontinued Operations (Schedule of Business Details and Line Items Comprising Discontinued Operations on Statements of Earnings and Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net sales		$ 104.4
Cost of goods sold		77.8
Gross profit		26.6
Selling, general and administrative expenses		22.0
Operating income		4.6
Interest expense		0.4
Other non-operating (income) expense, net		(1.2)
Earnings from discontinued operations before income tax		5.4
Income tax (benefit) expense		1.5
Net earnings from discontinued operations, net of tax	$ 0.5	3.9
Gain (loss) from disposal of discontinued businesses, before income tax	2.2	(17.7)
Income tax expense (benefit)		(0.4)
Gain (loss) from disposal of discontinued businesses, net of tax	2.2	(17.3)
Net gain (loss) from discontinued operations	2.7	(13.4)
EMEA and Pacific Rim Business [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net sales	96.9	104.4
Cost of goods sold	75.7	77.8
Gross profit	21.2	26.6
Selling, general and administrative expenses	20.8	22.0
Operating income	0.4	4.6
Interest expense		0.4
Other non-operating (income) expense, net		(1.2)
Earnings from discontinued operations before income tax	0.4	5.4
Income tax (benefit) expense	(0.1)	1.5
Net earnings from discontinued operations, net of tax	0.5	3.9
Gain (loss) from disposal of discontinued businesses, before income tax	2.2	(17.7)
Gain (loss) from disposal of discontinued businesses, net of tax	2.2	(17.7)	$ (19.3)	$ (74.0)
Net gain (loss) from discontinued operations	$ 2.7	(13.8)
Flooring Businesses [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Income tax expense (benefit)		(0.4)
Gain (loss) from disposal of discontinued businesses, net of tax		0.4
Net gain (loss) from discontinued operations		$ 0.4