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, 2014	$ 649.1	$ 0.6	$ 1,134.4	$ 271.0	$ (261.4)	$ (495.5)
Balance at Dec. 31, 2014		55,126,153
Balance at Dec. 31, 2014					5,057,382
Stock issuance, net		232,911
Share-based employee compensation	17.4		17.4
Net earnings	94.2			94.2
Other comprehensive income	8.1					8.1
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 issuance, net		180,694
Share-based employee compensation	9.2		9.2
Net earnings	104.7			104.7
Other comprehensive income	23.6					23.6
Separation of Armstrong Flooring, Inc.	(596.1)		(656.1)			60.0
Acquisition of treasury stock	(43.8)	$ (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	54,428,233
Balance at Dec. 31, 2016	6,168,907				6,168,907
Cumulative effect impact of ASU 2016-09 adoption	$ 8.7			8.7
Stock issuance, net		185,596
Share-based employee compensation	11.4		11.4
Net earnings	154.8			154.8
Other comprehensive income	57.9					57.9
Separation of Armstrong Flooring, Inc.	0.5		0.5
Acquisition of treasury stock	(80.4)	$ (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