| Document And Entity Information | Jul. 29, 2019 |
| Document And Entity Information [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Jul. 29, 2019 |
| Entity Registrant Name | ARMSTRONG WORLD INDUSTRIES INC |
| Entity Central Index Key | 0000007431 |
| Entity Emerging Growth Company | false |
| Trading Symbol | AWI |
| Entity File Number | 1-2116 |
| Entity Tax Identification Number | 230366390 |
| Entity Address, Address Line One | 2500 Columbia Avenue P.O. Box 3001 |
| Entity Address, City or Town | Lancaster |
| Entity Address, State or Province | Pennsylvania |
| Entity Address, Postal Zip Code | 17603 |
| City Area Code | (717) |
| Local Phone Number | 397-0611 |
