Consolidated Statements Of Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2015	$ 768.8	$ 0.6	$ 1,151.8	$ 365.2	$ (261.4)	$ (487.4)
Balance at Dec. 31, 2015		55,359,064
Balance at Dec. 31, 2015					5,057,382
Stock issuances, net		180,694
Share-based employee compensation	9.2		9.2
Net earnings	104.7			104.7
Other comprehensive income (loss)	23.6					23.6
Separation of Armstrong Flooring, Inc.	(596.1)		(656.1)			60.0
Acquisition of treasury stock	(43.8)				$ (43.8)
Acquisition of treasury stock, shares		(1,111,525)			1,111,525
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 issuances, net		185,596
Share-based employee compensation	11.4		11.4
Net earnings	154.8			154.8
Other comprehensive income (loss)	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	$ 419.3	$ 0.6	516.8	633.4	$ (385.6)	(345.9)
Balance at Dec. 31, 2017	52,772,139	52,772,139
Balance at Dec. 31, 2017	8,010,597				8,010,597
Cumulative effect impact of ASU adoption | ASU 2018-02 [Member]	$ (54.3)			54.3		(54.3)
Stock issuances, net		770,988
Share-based employee compensation	30.6		30.6
Cash dividends - $0.175 per common share	(8.6)			(8.6)
Net earnings	185.9			185.9
Other comprehensive income (loss)	(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	$ 261.2	$ 0.6	$ 547.4	$ 865.0	$ (692.2)	$ (459.6)
Balance at Dec. 31, 2018	48,808,239	48,808,239
Balance at Dec. 31, 2018	12,745,485				12,745,485