Business and Basis of Presentation (Narrative) (Details) $ in Millions		3 Months Ended		9 Months Ended
	Apr. 02, 2016 entity	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Business And Basis Of Presentation [Line Items]
Separation costs		$ 2.0	$ 7.4	$ 33.0	$ 16.8
Common stock split ratio of AFI share to two AWI shares	0.5
Number of independent publicly-traded companies from separation | entity	2
ASU 2015-03 And 2015-15 [Member]
Business And Basis Of Presentation [Line Items]
Reduction to other non-current assets and decrease to long-term debt						$ 4.1	$ 4.7