Condensed Consolidated Statements Of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive (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 issuance		125,919
Share-based employee compensation	7.0		7.0
Net earnings (loss)	7.0			7.0
Separation of Armstrong Flooring, Inc.	(585.1)		(641.9)			56.8
Other comprehensive income	4.7					4.7
Balance at Jun. 30, 2016	202.4	$ 0.6	516.9	372.2	$ (261.4)	(425.9)
Balance at Jun. 30, 2016		55,484,983
Balance at Jun. 30, 2016					5,057,382
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		112,176
Share-based employee compensation	3.8		3.8
Net earnings (loss)	71.7			71.7
Separation of Armstrong Flooring, Inc.	0.9		0.9
Other comprehensive income	16.7					16.7
Acquisition of treasury stock	(70.9)				$ (70.9)
Acquisition of treasury stock, shares		(1,659,452)			1,659,452
Balance at Jun. 30, 2017	$ 297.3	$ 0.6	$ 509.6	$ 550.3	$ (376.1)	$ (387.1)
Balance at Jun. 30, 2017	52,880,957	52,880,957
Balance at Jun. 30, 2017	7,828,359				7,828,359