Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Restated [Member]	Common Stock	Additional Paid-In Capital	Retained Earnings Restated [Member]	Treasury Stock	AOCI Attributable to Parent
Balance at Dec. 31, 2016		$ 266.4	$ 0.6	$ 504.9	$ 469.9	$ (305.2)	$ (403.8)
Balance at Dec. 31, 2016			54,428,233
Balance at Dec. 31, 2016						6,168,907
Cumulative effect impact of ASU adoption | ASU 2016-09 [Member]		8.7			8.7
Stock issuance, net			185,596
Share-based employee compensation		11.4		11.4
Net earnings	$ 119.6	119.6			119.6
Other comprehensive income (loss)	57.9	57.9					57.9
Separation of Armstrong Flooring, Inc.		0.5		0.5
Acquisition of treasury stock		(80.4)				$ (80.4)
Acquisition of treasury stock, shares			(1,841,690)			1,841,690
Balance at Dec. 31, 2017		384.1	$ 0.6	516.8	598.2	$ (385.6)	(345.9)
Balance at Dec. 31, 2017			52,772,139
Balance at Dec. 31, 2017						8,010,597
Cumulative effect impact of ASU adoption | ASU 2018-02 [Member]	(54.3)				54.3		(54.3)
Stock issuance, net			770,988
Cash dividends - per common share		(8.6)			(8.6)
Share-based employee compensation		30.6		30.6
Net earnings	185.9	185.9			185.9
Other comprehensive income (loss)	(59.4)	(59.4)					(59.4)
Acquisition of treasury stock		(306.6)				$ (306.6)
Acquisition of treasury stock, shares			(4,734,888)			4,734,888
Balance at Dec. 31, 2018	$ 226.0	226.0	$ 0.6	547.4	829.8	$ (692.2)	(459.6)
Balance at Dec. 31, 2018	48,808,239		48,808,239
Balance at Dec. 31, 2018						12,745,485
Cumulative effect impact of ASU adoption | ASU 2017-12 [Member]	$ 0.1				(0.1)		0.1
Stock issuance, net			709,671
Cash dividends - per common share		(36.0)			(36.0)
Share-based employee compensation		8.3		8.3
Net earnings	214.5	214.5			214.5
Other comprehensive income (loss)	83.4	83.4					83.4
Acquisition of treasury stock		(131.3)				$ (131.3)
Acquisition of treasury stock, shares			(1,525,562)			1,525,562
Balance at Dec. 31, 2019	$ 364.9	$ 364.9	$ 0.6	$ 555.7	$ 1,008.2	$ (823.5)	$ (376.1)
Balance at Dec. 31, 2019	47,992,348		47,992,348
Balance at Dec. 31, 2019						14,271,047