| Document And Entity Information | Oct. 23, 2019 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 23, 2019 |
| Entity Registrant Name | ARMSTRONG WORLD INDUSTRIES INC |
| Entity Central Index Key | 0000007431 |
| Entity Emerging Growth Company | false |
| Entity File Number | 1-2116 |
| Entity Incorporation, State or Country Code | PA |
| Entity Tax Identification Number | 23-0366390 |
| Entity Address, Address Line One | 2500 Columbia Avenue P.O. Box 3001 |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of each class | Common Stock, $0.01 par value per share |
| Trading Symbol(s) | AWI |
| Name of each exchange on which registered | NYSE |
