Business And Chapter 11 Reorganization (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended	1 Months Ended	3 Months Ended				1 Months Ended
	Dec. 31, 2013	Aug. 31, 2009 Asbestos PI Trust And TPG [Member]	Dec. 31, 2013 Asbestos PI Trust And TPG [Member]	Sep. 30, 2013 Asbestos PI Trust And TPG [Member]	Dec. 31, 2012 Asbestos PI Trust And TPG [Member]	Dec. 31, 2013 Minimum [Member] Asbestos PI Trust And TPG [Member]	Aug. 31, 2009 Additional Economic Interest [Member] Asbestos PI Trust And TPG [Member]
Business And Basis Of Presentation [Line Items]
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. 02, 2006
Entity arising from bankruptcy proceeding	Asbestos Personal Injury Settlement Trust ("Asbestos PI Trust")
Purchase of common stock by major shareholder		7,000,000					1,039,777
Sale of stock by investee			6,000,000	12,057,382	5,980,000
Payment to acquire shares held in treasury	$ 261.4
Treasury shares acquired	5,057,382
Holding percentage in Armstrong World Industries, Inc.						25.00%