Business And Basis Of Presentation (Details) $ in Millions		3 Months Ended	9 Months Ended	27 Months Ended
	Feb. 23, 2015 entity	Sep. 30, 2015 USD ($)	Sep. 30, 2015 USD ($) shares	Dec. 31, 2014 shares
Business And Basis Of Presentation [Line Items]
Number of independent publicly-traded companies from separation | entity	2
Separation costs		$ 7.4	$ 16.8
Bankruptcy voluntary petition filed for relief date			Dec. 01, 2000
Bankruptcy court where petition filed			United States Bankruptcy Court for the District of Delaware
Plan of reorganization approved date			Oct. 01, 2006
Entity arising from bankruptcy proceeding			AWI emerged from Chapter 11
Creation of settlement trust date			October 2006
Name of the settlement trust			Asbestos Personal Injury Settlement Trust (the "Asbestos PI Trust")
Asbestos PI Trust [Member]
Business And Basis Of Presentation [Line Items]
Sale of stock by investee | shares			4,281,884	20,448,362
Holding percentage in Armstrong World Industries, Inc.		9.00%	9.00%