Business (Details) $ in Millions		9 Months Ended	12 Months Ended	27 Months Ended
	Feb. 23, 2015 entity	Sep. 30, 2015 shares	Dec. 31, 2015 USD ($)	Dec. 31, 2014 shares	Oct. 01, 2006 shares
Business And Basis Of Presentation [Line Items]
Number of independent publicly-traded companies from separation | entity	2
Separation costs | $			$ 34.3
Plan of reorganization approved date			Feb. 23, 2015
Creation of settlement trust date			October 2006
Name of the settlement trust			Asbestos Personal Injury Settlement Trust ("Asbestos PI Trust")
Asbestos PI Trust [Member]
Business And Basis Of Presentation [Line Items]
Common stock shares issued to Asbestos PI Trust					37,000,000
Sale of stock by investee		4,281,884		20,448,362
Holding percentage in Armstrong World Industries, Inc.			9.00%