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Cover - shares
 3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2021
Oct. 29, 2021
Cover [Abstract]      
Document Type   10-Q  
Document Quarterly Report true    
Document Period End Date Sep. 30, 2021    
Document Transition Report   false  
Entity File Number   1-10258  
Entity Registrant Name   Tredegar Corporation  
Entity Incorporation, State or Country Code VA    
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  
Title of 12(b) Security Common stock, no par value    
Trading Symbol TG    
Security Exchange Name NYSE    
Entity Current Reporting Status   Yes  
Entity Interactive Data Current   Yes  
Entity Filer Category Accelerated Filer    
Entity Small Business   false  
Entity Emerging Growth Company   false  
Entity Shell Company   false  
Entity Common Stock, Shares Outstanding     33,742,316
Entity Central Index Key   0000850429  
Current Fiscal Year End Date   --12-31  
Document Fiscal Year Focus   2021  
Document Fiscal Period Focus   Q3  
Amendment Flag   false