Business And Basis Of Presentation (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	27 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Business And Basis Of Presentation [Line Items]
Separation costs	4.3
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	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	2,739,944	20,448,362
Holding percentage in Armstrong World Industries, Inc.	12.00%