| Document And Entity Information | Oct. 27, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K/A |
| Amendment Flag | true |
| Amendment Description | On October 27, 2020, Armstrong World Industries, Inc. (the “Company”) issued a press release announcing its third quarter 2020 consolidated financial results and earnings outlook for fiscal year 2020, together with an earnings call presentation, and furnished the press release and earnings call presentation on a Current Report on Form 8-K (the “Original Report”). The Company is filing this Amendment No. 1 to Current Report on Form 8-K/A (this “Amended Report”) solely to furnish a copy of: (i) a corrected press release reflecting updated projected information for depreciation, net loss and EPS on page 13 as Exhibit 99.1, and (ii) a corrected earnings call presentation reflecting updated projected information for EPS on page 12, depreciation on page 18 and net loss on page 19 as Exhibit 99.2. Exhibit 99.1 and Exhibit 99.2 of this Amended Report supersede and replace in their entirety Exhibit 99.1 and Exhibit 99.2, respectively, to the Original Report. Except as identified above, no other information in the press release or earnings call presentation furnished with the Original Report has been updated. |
| Document Period End Date | Oct. 27, 2020 |
| Entity Registrant Name | ARMSTRONG WORLD INDUSTRIES, INC. |
| Entity Central Index Key | 0000007431 |
| Entity Emerging Growth Company | false |
| Entity File Number | 1-2116 |
| 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 |
| Entity Incorporation, State or Country Code | PA |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.01 par value per share |
| Trading Symbol | AWI |
| Security Exchange Name | NYSE |
