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Document And Entity Information - USD ($)
$ in Billions
 12 Months Ended
Dec. 31, 2019
Feb. 18, 2020
Jun. 28, 2019
Cover [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2019    
Document Fiscal Year Focus 2019    
Document Fiscal Period Focus FY    
Entity Registrant Name ARMSTRONG WORLD INDUSTRIES, INC.    
Trading Symbol AWI    
Entity Central Index Key 0000007431    
Current Fiscal Year End Date --12-31    
Entity Filer Category Large Accelerated Filer    
Entity Shell Company false    
Entity File Number 1-2116    
Entity Tax Identification Number 23-0366390    
Entity Address, Address Line One 2500 Columbia Avenue    
Entity Address, City or Town Lancaster    
Entity Address, State or Province PA    
Entity Address, Postal Zip Code 17603    
City Area Code 717    
Local Phone Number 397-0611    
Entity Emerging Growth Company false    
Entity Small Business false    
Document Annual Report true    
Title of 12(b) Security Common Stock, $0.01 par value per share    
Security Exchange Name NYSE    
Entity Incorporation, State or Country Code PA    
Document Transition Report false    
Entity Interactive Data Current Yes    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Common Stock, Shares Outstanding   47,987,627  
Entity Public Float     $ 4.7
Documents Incorporated by Reference

Documents Incorporated by Reference

Certain sections of Armstrong World Industries, Inc.’s definitive Proxy Statement for use in connection with its 2020 annual meeting of shareholders, to be filed no later than April 29, 2020 (120 days after the last day of our 2019 fiscal year), are incorporated by reference into Part III of this Form 10-K Report where indicated.