| Document and Entity Information | May 06, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | May 6, 2021 |
| Entity Registrant Name | TREDEGAR CORP |
| Entity Incorporation, State or Country Code | VA |
| Entity File Number | 001-10258 |
| Entity Tax Identification Number | 54-1497771 |
| Entity Address, Address Line One | 1100 BOULDERS PARKWAY |
| Entity Address, City or Town | RICHMOND |
| Entity Address, State or Province | VA |
| Entity Address, Postal Zip Code | 23225 |
| City Area Code | 804 |
| Local Phone Number | 330-1000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000850429 |
| Title of 12(b) Security | Common stock, no par value |
| Trading Symbol | TG |
| Security Exchange Name | NYSE |
